diff --git a/docs-2.0/3.ngql-guide/10.tag-statements/3.alter-tag.md b/docs-2.0/3.ngql-guide/10.tag-statements/3.alter-tag.md
index 83ba5ee859a..1b17fc7a2a8 100644
--- a/docs-2.0/3.ngql-guide/10.tag-statements/3.alter-tag.md
+++ b/docs-2.0/3.ngql-guide/10.tag-statements/3.alter-tag.md
@@ -19,9 +19,9 @@ ALTER TAG <tag_name>
     [DEFAULT <defalut_value>];
 
 alter_definition:
-| ADD    (prop_name data_type)
+| ADD    (prop_name data_type [NULL | NOT NULL] [DEFAULT <default_value>] [COMMENT '<comment>'])
 | DROP   (prop_name)
-| CHANGE (prop_name data_type)
+| CHANGE (prop_name data_type [NULL | NOT NULL] [DEFAULT <default_value>] [COMMENT '<comment>'])
 
 ttl_definition:
     TTL_DURATION = ttl_duration, TTL_COL = prop_name
@@ -37,8 +37,8 @@ ttl_definition:
 nebula> CREATE TAG IF NOT EXISTS t1 (p1 string, p2 int);
 nebula> ALTER TAG t1 ADD (p3 int, p4 string);
 nebula> ALTER TAG t1 TTL_DURATION = 2, TTL_COL = "p2";
-nebula> ALTER TAG t1 COMMENT 'test1';
-nebula> ALTER TAG t1 ADD (p5 double NOT NULL DEFAULT 0.4 COMMENT 'Some comment')
+nebula> ALTER TAG t1 COMMENT='test1';
+nebula> ALTER TAG t1 ADD (p5 double NOT NULL DEFAULT 0.4 COMMENT 'p5') COMMENT='test2';
 ```
 
 ## Implementation of the operation