diff --git a/README.md b/README.md
index b8ac11e..1ae2f7a 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,8 @@
 This repository includes related files of following docker images:
  - OAP server
  - UI
+ 
+ Documents of each version are in `v-x.y.z/oap` and `v-x.y.z/ui`. Such as [6.4 OAP](6/6.4/oap) and [6.4 UI](6/6.4/ui)
 
 The convenience images are published in docker hub.
 - https://hub.docker.com/r/apache/skywalking-base