diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index e0351784ff9ea1f4bb76f0ef865abb89c7518fbe..447de9de93ebffa7103c3913bd9257ac1095a410 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -6031,12 +6031,7 @@ int32_t setAlterTableInfo(SSqlObj* pSql, struct SSqlInfo* pInfo) {
     }
 
     int32_t schemaLen = sizeof(STColumn) * numOfTags;
-    int32_t size = 0;
-    if (pTagsSchema->type == TSDB_DATA_TYPE_JSON){
-      size = sizeof(SUpdateTableTagValMsg) + pTagsSchema->bytes + schemaLen + TSDB_EXTRA_PAYLOAD_SIZE;
-    } else {
-      size = sizeof(SUpdateTableTagValMsg) + TSDB_MAX_TAGS_LEN + schemaLen + TSDB_EXTRA_PAYLOAD_SIZE;
-    }
+    int32_t size = = sizeof(SUpdateTableTagValMsg) + pTagsSchema->bytes + schemaLen + TSDB_EXTRA_PAYLOAD_SIZE;
 
     if (TSDB_CODE_SUCCESS != tscAllocPayload(pCmd, size)) {
       tscError("0x%"PRIx64" failed to malloc for alter table pMsg", pSql->self);
@@ -6099,10 +6094,10 @@ int32_t setAlterTableInfo(SSqlObj* pSql, struct SSqlInfo* pInfo) {
     }
 
     int32_t len = 0;
-    if (!IS_VAR_DATA_TYPE(pTagsSchema->type)) {
-      len = tDataTypes[pTagsSchema->type].bytes;
-    } else if(pTagsSchema->type == TSDB_DATA_TYPE_JSON){
+    if(pTagsSchema->type == TSDB_DATA_TYPE_JSON){
       len = kvRowLen(pUpdateMsg->data + schemaLen);
+    }else if (!IS_VAR_DATA_TYPE(pTagsSchema->type)) {
+      len = tDataTypes[pTagsSchema->type].bytes;
     } else {
       len = varDataTLen(pUpdateMsg->data + schemaLen);
       if(len > pTagsSchema->bytes) return invalidOperationMsg(pMsg, msg14);
diff --git a/tests/pytest/stable/json_tag.py b/tests/pytest/stable/json_tag.py
index 36fc03f23d97facce7dd8322053ff97bc02373ca..774a5570821ca491c4de3547c1247156cbd6dbd8 100644
--- a/tests/pytest/stable/json_tag.py
+++ b/tests/pytest/stable/json_tag.py
@@ -33,8 +33,8 @@ class TDTestCase:
         #tdSql.execute("create table if not exists db_json_tag_test.jsons1(ts timestamp, dataInt int, dataStr nchar(50)) tags(jtag json)")
         #tdSql.execute("CREATE TABLE if not exists db_json_tag_test.jsons1_1 using db_json_tag_test.jsons1 tags('{\"loc\":\"fff\",\"id\":5}')")
         #tdSql.execute("CREATE TABLE if not exists db_json_tag_test.jsons1_3 using db_json_tag_test.jsons1 tags(3333)")
-        #tdSql.execute("insert into jsons1_2 using db_json_tag_test.jsons1 tags('{\"num\":5,\"location\":\"beijing\"}' values (now, 1, 'sss')")
-        #tdSql.execute("insert into jsons1_4 using db_json_tag_test.jsons1 tags(3)")
+        #tdSql.execute("insert into db_json_tag_test.jsons1_2 using db_json_tag_test.jsons1 tags('{\"num\":5,\"location\":\"beijing\"}' values (now, 1, 'sss')")
+        #tdSql.execute("insert into db_json_tag_test.jsons1_4 using db_json_tag_test.jsons1 tags(3)")
 
         print("==============step2")
         tdLog.info("select table")