diff --git a/src/main/java/com/starrocks/connector/flink/row/sink/StarRocksTableRowTransformer.java b/src/main/java/com/starrocks/connector/flink/row/sink/StarRocksTableRowTransformer.java
index aef0c02b..9fa5f2e7 100644
--- a/src/main/java/com/starrocks/connector/flink/row/sink/StarRocksTableRowTransformer.java
+++ b/src/main/java/com/starrocks/connector/flink/row/sink/StarRocksTableRowTransformer.java
@@ -130,8 +130,10 @@ private Object typeConvertion(LogicalType type, RowData record, int pos) {
                 }
                 StarRocksDataType starRocksDataType =
                         columns.getOrDefault(columnNames[pos], StarRocksDataType.UNKNOWN);
-                if ((starRocksDataType == StarRocksDataType.JSON ||
-                        starRocksDataType == StarRocksDataType.UNKNOWN)
+                if (starRocksDataType == StarRocksDataType.UNKNOWN) {
+                    return sValue;
+                }
+                if ((starRocksDataType == StarRocksDataType.JSON)
                     && (sValue.charAt(0) == '{' || sValue.charAt(0) == '[')) {
                     // The json string need to be converted to a json object, and to the json string
                     // again via JSON.toJSONString in StarRocksJsonSerializer#serialize. Otherwise,