Update protobuf version in doc (#2618)
diff --git a/docs/cn/getting_started.md b/docs/cn/getting_started.md
index 9cb88de..a7b468b 100644
--- a/docs/cn/getting_started.md
+++ b/docs/cn/getting_started.md
@@ -341,11 +341,9 @@
无已知问题。
-## protobuf: 2.4+
+## protobuf: 3.0-3.25
-同一个文件兼容pb 3.x版本和pb 2.x版本：
-不要使用proto3新增的类型，并且在proto文件的起始位置添加`syntax=proto2;`声明。
-[tools/add_syntax_equal_proto2_to_all.sh](https://github.com/apache/brpc/blob/master/tools/add_syntax_equal_proto2_to_all.sh)这个脚本可以给所有没有这行声明的proto文件添加`syntax="proto2"`声明。
+[1.8.0版本](https://github.com/apache/brpc/releases/tag/1.8.0)中[#2406](https://github.com/apache/brpc/pull/2406)和[#2493](https://github.com/apache/brpc/pull/2493)引入了部分proto3语法，所以目前bRPC不再兼容pb 2.x版本。如果你希望使用pb 2.x版本，可以使用1.8.0之前的bRPC版本。
pb 3.x中的Arena至今没被支持。
diff --git a/docs/en/getting_started.md b/docs/en/getting_started.md
index 575f4de..317a9f7 100644
--- a/docs/en/getting_started.md
+++ b/docs/en/getting_started.md
@@ -338,11 +338,9 @@
no known issues.
-## protobuf: 2.4+
+## protobuf: 3.0-3.25
-Be compatible with pb 3.x and pb 2.x with the same file:
-Don't use new types in proto3 and start the proto file with `syntax="proto2";`
-[tools/add_syntax_equal_proto2_to_all.sh](https://github.com/apache/brpc/blob/master/tools/add_syntax_equal_proto2_to_all.sh)can add `syntax="proto2"` to all proto files without it.
+[#2406](https://github.com/apache/brpc/pull/2406) and [#2493](https://github.com/apache/brpc/pull/2493) in [version 1.8.0]((https://github.com/apache/brpc/releases/tag/1.8.0)) introduce some proto3 syntax, so currently bRPC is no longer compatible with pb 2.x version. If you want to use pb 2.x version, you can use bRPC version before 1.8.0.
Arena in pb 3.x is not supported yet.
