diff --git a/sql-statements/sql-statement-create-index.md b/sql-statements/sql-statement-create-index.md
index 2e5f5ee76032f..19d4efecc512c 100644
--- a/sql-statements/sql-statement-create-index.md
+++ b/sql-statements/sql-statement-create-index.md
@@ -111,18 +111,6 @@ Query OK, 0 rows affected (0.31 sec)
 
 ## Expression index
 
-> **Warning:**
->
-> Expression index is still an experimental feature. It is **NOT** recommended that you use it in the production environment.
-
-To use this feature, make the following setting in [TiDB Configuration File](/tidb-configuration-file.md#allow-expression-index-new-in-v400):
-
-{{< copyable "sql" >}}
-
-```sql
-allow-expression-index = true
-```
-
 TiDB can build indexes not only on one or more columns in a table, but also on an expression. When queries involve expressions, expression indexes can speed up those queries.
 
 Take the following query as an example:
diff --git a/tidb-configuration-file.md b/tidb-configuration-file.md
index 274f5e265e34b..02974975d3225 100644
--- a/tidb-configuration-file.md
+++ b/tidb-configuration-file.md
@@ -558,15 +558,4 @@ For pessimistic transaction usage, refer to [TiDB Pessimistic Transaction Mode](
 
 ## experimental
 
-The `experimental` section describes configurations related to the experimental features of TiDB. This section is introduced since v3.1.0.
-
-### `allow-auto-random` <span class="version-mark">New in v3.1.0</span>
-
-- Determines whether to allow using `AUTO_RANDOM`.
-- Default value: `false`
-- By default, TiDB does not support using `AUTO_RANDOM`. When the value is `true`, you cannot set `alter-primary-key` to `true` at the same time.
-
-### `allow-expression-index` <span class="version-mark">New in v4.0.0</span>
-
-- Determines whether to create the expression index.
-- Default value: `false`
+The `experimental` section, introduced in v3.1.0, describes configurations related to the experimental features of TiDB. Currently, this section has no configuration item.