diff --git a/dubbo-common/src/main/java/org/apache/dubbo/common/extension/ExtensionLoader.java b/dubbo-common/src/main/java/org/apache/dubbo/common/extension/ExtensionLoader.java
index 820dbd9..d85a34c 100644
--- a/dubbo-common/src/main/java/org/apache/dubbo/common/extension/ExtensionLoader.java
+++ b/dubbo-common/src/main/java/org/apache/dubbo/common/extension/ExtensionLoader.java
@@ -42,6 +42,7 @@
 import java.util.Collections;
 import java.util.Enumeration;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.LinkedHashSet;
 import java.util.LinkedList;
 import java.util.List;
@@ -148,7 +149,8 @@
 
     private ExtensionLoader(Class<?> type) {
         this.type = type;
-        objectFactory = (type == ExtensionFactory.class ? null : ExtensionLoader.getExtensionLoader(ExtensionFactory.class).getAdaptiveExtension());
+        objectFactory =
+                (type == ExtensionFactory.class ? null : ExtensionLoader.getExtensionLoader(ExtensionFactory.class).getAdaptiveExtension());
     }
 
     private static <T> boolean withExtensionAnnotation(Class<T> type) {
@@ -270,6 +272,7 @@
         List<T> activateExtensions = new ArrayList<>();
         // solve the bug of using @SPI's wrapper method to report a null pointer exception.
         TreeMap<Class, T> activateExtensionsMap = new TreeMap<>(ActivateComparator.COMPARATOR);
+        Set<String> loadedNames = new HashSet<>();
         Set<String> names = CollectionUtils.ofSet(values);
         if (!names.contains(REMOVE_VALUE_PREFIX + DEFAULT_KEY)) {
             getExtensionClasses();
@@ -291,11 +294,13 @@
                 if (isMatchGroup(group, activateGroup)
                         && !names.contains(name)
                         && !names.contains(REMOVE_VALUE_PREFIX + name)
-                        && isActive(activateValue, url)) {
+                        && isActive(activateValue, url)
+                        && !loadedNames.contains(name)) {
                     activateExtensionsMap.put(getExtensionClass(name), getExtension(name));
+                    loadedNames.add(name);
                 }
             }
-            if(!activateExtensionsMap.isEmpty()){
+            if (!activateExtensionsMap.isEmpty()) {
                 activateExtensions.addAll(activateExtensionsMap.values());
             }
         }
@@ -303,13 +308,21 @@
         for (String name : names) {
             if (!name.startsWith(REMOVE_VALUE_PREFIX)
                     && !names.contains(REMOVE_VALUE_PREFIX + name)) {
-                if (DEFAULT_KEY.equals(name)) {
-                    if (!loadedExtensions.isEmpty()) {
-                        activateExtensions.addAll(0, loadedExtensions);
-                        loadedExtensions.clear();
+                if (!loadedNames.contains(name)) {
+                    if (DEFAULT_KEY.equals(name)) {
+                        if (!loadedExtensions.isEmpty()) {
+                            activateExtensions.addAll(0, loadedExtensions);
+                            loadedExtensions.clear();
+                        }
+                    } else {
+                        loadedExtensions.add(getExtension(name));
                     }
+                    loadedNames.add(name);
                 } else {
-                    loadedExtensions.add(getExtension(name));
+                    // If getExtension(name) exists, getExtensionClass(name) must exist, so there is no null pointer processing here.
+                    String simpleName = getExtensionClass(name).getSimpleName();
+                    logger.warn("Catch duplicated filter, ExtensionLoader will ignore one of them. Please check. Filter Name: " + name +
+                            ". Ignored Class Name: " + simpleName);
                 }
             }
         }
@@ -785,8 +798,10 @@
         Map<String, Class<?>> extensionClasses = new HashMap<>();
 
         for (LoadingStrategy strategy : strategies) {
-            loadDirectory(extensionClasses, strategy.directory(), type.getName(), strategy.preferExtensionClassLoader(), strategy.overridden(), strategy.excludedPackages());
-            loadDirectory(extensionClasses, strategy.directory(), type.getName().replace("org.apache", "com.alibaba"), strategy.preferExtensionClassLoader(), strategy.overridden(), strategy.excludedPackages());
+            loadDirectory(extensionClasses, strategy.directory(), type.getName(), strategy.preferExtensionClassLoader(),
+                    strategy.overridden(), strategy.excludedPackages());
+            loadDirectory(extensionClasses, strategy.directory(), type.getName().replace("org.apache", "com.alibaba"),
+                    strategy.preferExtensionClassLoader(), strategy.overridden(), strategy.excludedPackages());
         }
 
         return extensionClasses;
@@ -879,7 +894,9 @@
                                 loadClass(extensionClasses, resourceURL, Class.forName(clazz, true, classLoader), name, overridden);
                             }
                         } catch (Throwable t) {
-                            IllegalStateException e = new IllegalStateException("Failed to load extension class (interface: " + type + ", class line: " + line + ") in " + resourceURL + ", cause: " + t.getMessage(), t);
+                            IllegalStateException e = new IllegalStateException(
+                                    "Failed to load extension class (interface: " + type + ", class line: " + line + ") in " + resourceURL +
+                                            ", cause: " + t.getMessage(), t);
                             exceptions.put(line, e);
                         }
                     }
@@ -918,7 +935,8 @@
             if (StringUtils.isEmpty(name)) {
                 name = findAnnotationName(clazz);
                 if (name.length() == 0) {
-                    throw new IllegalStateException("No such extension name for the class " + clazz.getName() + " in the config " + resourceURL);
+                    throw new IllegalStateException(
+                            "No such extension name for the class " + clazz.getName() + " in the config " + resourceURL);
                 }
             }
 
@@ -952,7 +970,8 @@
         } else if (c != clazz) {
             // duplicate implementation is unacceptable
             unacceptableExceptions.add(name);
-            String duplicateMsg = "Duplicate extension " + type.getName() + " name " + name + " on " + c.getName() + " and " + clazz.getName();
+            String duplicateMsg =
+                    "Duplicate extension " + type.getName() + " name " + name + " on " + c.getName() + " and " + clazz.getName();
             logger.error(duplicateMsg);
             throw new IllegalStateException(duplicateMsg);
         }
@@ -969,7 +988,8 @@
             cachedActivates.put(name, activate);
         } else {
             // support com.alibaba.dubbo.common.extension.Activate
-            com.alibaba.dubbo.common.extension.Activate oldActivate = clazz.getAnnotation(com.alibaba.dubbo.common.extension.Activate.class);
+            com.alibaba.dubbo.common.extension.Activate oldActivate =
+                    clazz.getAnnotation(com.alibaba.dubbo.common.extension.Activate.class);
             if (oldActivate != null) {
                 cachedActivates.put(name, oldActivate);
             }
@@ -1049,7 +1069,8 @@
     private Class<?> createAdaptiveExtensionClass() {
         String code = new AdaptiveClassCodeGenerator(type, cachedDefaultName).generate();
         ClassLoader classLoader = findClassLoader();
-        org.apache.dubbo.common.compiler.Compiler compiler = ExtensionLoader.getExtensionLoader(org.apache.dubbo.common.compiler.Compiler.class).getAdaptiveExtension();
+        org.apache.dubbo.common.compiler.Compiler compiler =
+                ExtensionLoader.getExtensionLoader(org.apache.dubbo.common.compiler.Compiler.class).getAdaptiveExtension();
         return compiler.compile(code, classLoader);
     }
 
diff --git a/dubbo-common/src/test/java/org/apache/dubbo/common/extension/ExtensionLoaderTest.java b/dubbo-common/src/test/java/org/apache/dubbo/common/extension/ExtensionLoaderTest.java
index 0537836..9ebfc03 100644
--- a/dubbo-common/src/test/java/org/apache/dubbo/common/extension/ExtensionLoaderTest.java
+++ b/dubbo-common/src/test/java/org/apache/dubbo/common/extension/ExtensionLoaderTest.java
@@ -174,7 +174,8 @@
             getExtensionLoader(SimpleExt.class).getExtension("XXX");
             fail();
         } catch (IllegalStateException expected) {
-            assertThat(expected.getMessage(), containsString("No such extension org.apache.dubbo.common.extension.ext1.SimpleExt by name XXX"));
+            assertThat(expected.getMessage(),
+                    containsString("No such extension org.apache.dubbo.common.extension.ext1.SimpleExt by name XXX"));
         }
     }
 
@@ -184,7 +185,8 @@
             getExtensionLoader(WrappedExt.class).getExtension("XXX");
             fail();
         } catch (IllegalStateException expected) {
-            assertThat(expected.getMessage(), containsString("No such extension org.apache.dubbo.common.extension.ext6_wrap.WrappedExt by name XXX"));
+            assertThat(expected.getMessage(),
+                    containsString("No such extension org.apache.dubbo.common.extension.ext6_wrap.WrappedExt by name XXX"));
         }
     }
 
@@ -257,7 +259,8 @@
             getExtensionLoader(AddExt1.class).getExtension("Manual1");
             fail();
         } catch (IllegalStateException expected) {
-            assertThat(expected.getMessage(), containsString("No such extension org.apache.dubbo.common.extension.ext8_add.AddExt1 by name Manual"));
+            assertThat(expected.getMessage(),
+                    containsString("No such extension org.apache.dubbo.common.extension.ext8_add.AddExt1 by name Manual"));
         }
 
         getExtensionLoader(AddExt1.class).addExtension("Manual1", AddExt1_ManualAdd1.class);
@@ -286,7 +289,8 @@
             getExtensionLoader(AddExt1.class).addExtension("impl1", AddExt1_ManualAdd1.class);
             fail();
         } catch (IllegalStateException expected) {
-            assertThat(expected.getMessage(), containsString("Extension name impl1 already exists (Extension interface org.apache.dubbo.common.extension.ext8_add.AddExt1)!"));
+            assertThat(expected.getMessage(), containsString(
+                    "Extension name impl1 already exists (Extension interface org.apache.dubbo.common.extension.ext8_add.AddExt1)!"));
         }
     }
 
@@ -309,7 +313,8 @@
             loader.addExtension(null, AddExt1_ManualAdaptive.class);
             fail();
         } catch (IllegalStateException expected) {
-            assertThat(expected.getMessage(), containsString("Adaptive Extension already exists (Extension interface org.apache.dubbo.common.extension.ext8_add.AddExt1)!"));
+            assertThat(expected.getMessage(), containsString(
+                    "Adaptive Extension already exists (Extension interface org.apache.dubbo.common.extension.ext8_add.AddExt1)!"));
         }
     }
 
@@ -319,7 +324,8 @@
             getExtensionLoader(AddExt1.class).getExtension("Manual2");
             fail();
         } catch (IllegalStateException expected) {
-            assertThat(expected.getMessage(), containsString("No such extension org.apache.dubbo.common.extension.ext8_add.AddExt1 by name Manual"));
+            assertThat(expected.getMessage(),
+                    containsString("No such extension org.apache.dubbo.common.extension.ext8_add.AddExt1 by name Manual"));
         }
 
         {
@@ -360,7 +366,8 @@
             getExtensionLoader(AddExt1.class).replaceExtension("NotExistedExtension", AddExt1_ManualAdd1.class);
             fail();
         } catch (IllegalStateException expected) {
-            assertThat(expected.getMessage(), containsString("Extension name NotExistedExtension doesn't exist (Extension interface org.apache.dubbo.common.extension.ext8_add.AddExt1)"));
+            assertThat(expected.getMessage(), containsString(
+                    "Extension name NotExistedExtension doesn't exist (Extension interface org.apache.dubbo.common.extension.ext8_add.AddExt1)"));
         }
     }
 
@@ -372,7 +379,8 @@
             loader.replaceExtension(null, AddExt4_ManualAdaptive.class);
             fail();
         } catch (IllegalStateException expected) {
-            assertThat(expected.getMessage(), containsString("Adaptive Extension doesn't exist (Extension interface org.apache.dubbo.common.extension.ext8_add.AddExt4)"));
+            assertThat(expected.getMessage(), containsString(
+                    "Adaptive Extension doesn't exist (Extension interface org.apache.dubbo.common.extension.ext8_add.AddExt4)"));
         }
     }
 
@@ -386,12 +394,25 @@
             loader.getExtension("error");
             fail();
         } catch (IllegalStateException expected) {
-            assertThat(expected.getMessage(), containsString("Failed to load extension class (interface: interface org.apache.dubbo.common.extension.ext7.InitErrorExt"));
+            assertThat(expected.getMessage(), containsString(
+                    "Failed to load extension class (interface: interface org.apache.dubbo.common.extension.ext7.InitErrorExt"));
             assertThat(expected.getMessage(), containsString("java.lang.ExceptionInInitializerError"));
         }
     }
 
     @Test
+    public void testLoadActivateExtensionWithNoRepeat() {
+        URL url = URL.valueOf("test://localhost/test");
+        List<ActivateExt1> list = getExtensionLoader(ActivateExt1.class)
+                .getActivateExtension(url, new String[] {"old1", "old2"}, "default_group");
+        Assertions.assertEquals(3, list.size());
+
+        list = getExtensionLoader(ActivateExt1.class)
+                .getActivateExtension(url, new String[] {"old1", "old2", "old1"}, "default_group");
+        Assertions.assertEquals(3, list.size());
+    }
+
+    @Test
     public void testLoadActivateExtension() throws Exception {
         // test default
         URL url = URL.valueOf("test://localhost/test");