diff --git a/docs/config/index.md b/docs/config/index.md
index f89581fc922932..79d282fb51a0a3 100644
--- a/docs/config/index.md
+++ b/docs/config/index.md
@@ -688,6 +688,10 @@ export default defineConfig({
 
   If disabled, all CSS in the entire project will be extracted into a single CSS file.
 
+  ::: tip Note
+  If you specify `build.lib`, `build.cssCodeSplit` will be `false` as default.
+  :::
+
 ### build.cssTarget
 
 - **Type:** `string | string[]`