diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index 7adc0812ae12bd8711cba5988806a4c7ba740cf5..5539c627a80c81b6d380b8af6a001fd9db994636 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -5884,6 +5884,11 @@ int32_t setAlterTableInfo(SSqlObj* pSql, struct SSqlInfo* pInfo) {
 
     tVariantListItem* pItem = taosArrayGet(pVarList, 1);
     SSchema* pTagsSchema = tscGetTableColumnSchema(pTableMetaInfo->pTableMeta, columnIndex.columnIndex);
+
+    if (pItem->pVar.nLen > pTagsSchema->bytes * TSDB_NCHAR_SIZE) {
+      return invalidOperationMsg(pMsg, msg14);
+    }
+
     pAlterSQL->tagData.data = calloc(1, pTagsSchema->bytes * TSDB_NCHAR_SIZE + VARSTR_HEADER_SIZE);
 
     if (tVariantDump(&pItem->pVar, pAlterSQL->tagData.data, pTagsSchema->type, true) != TSDB_CODE_SUCCESS) {