diff --git a/src/client/src/tscSubquery.c b/src/client/src/tscSubquery.c
index 3a205924bf934ddb3ddf85604f349cbd9431c85c..8c741dfdc88906be04b2cece45ac27a4a76fbfc1 100644
--- a/src/client/src/tscSubquery.c
+++ b/src/client/src/tscSubquery.c
@@ -1888,11 +1888,14 @@ static void transferNcharData(SSqlObj *pSql, int32_t columnIndex, TAOS_FIELD *pF
     /* string terminated char for binary data*/
     memset(pRes->buffer[columnIndex], 0, pField->bytes + TSDB_NCHAR_SIZE);
     
-    if (taosUcs4ToMbs(pRes->tsrow[columnIndex], pField->bytes - VARSTR_HEADER_SIZE, pRes->buffer[columnIndex])) {
+    int32_t length = taosUcs4ToMbs(pRes->tsrow[columnIndex], pRes->length[columnIndex], pRes->buffer[columnIndex]);
+    if ( length >= 0 ) {
       pRes->tsrow[columnIndex] = pRes->buffer[columnIndex];
+      pRes->length[columnIndex] = length;
     } else {
       tscError("%p charset:%s to %s. val:%ls convert failed.", pSql, DEFAULT_UNICODE_ENCODEC, tsCharset, pRes->tsrow[columnIndex]);
       pRes->tsrow[columnIndex] = NULL;
+      pRes->length[columnIndex] = 0;
     }
   }
 }
diff --git a/src/util/inc/tutil.h b/src/util/inc/tutil.h
index 3a0a1920af4cb2dd841bbeadd973eea85830019e..5dcb6e406f5c8dccd989ec0e2e8e1d2542177020 100644
--- a/src/util/inc/tutil.h
+++ b/src/util/inc/tutil.h
@@ -145,7 +145,7 @@ bool taosMbsToUcs4(char *mbs, size_t mbs_len, char *ucs4, int32_t ucs4_max_len,
 
 int tasoUcs4Compare(void* f1_ucs4, void *f2_ucs4, int bytes);
 
-bool taosUcs4ToMbs(void *ucs4, int32_t ucs4_max_len, char *mbs);
+int32_t taosUcs4ToMbs(void *ucs4, int32_t ucs4_max_len, char *mbs);
 
 bool taosValidateEncodec(const char *encodec);
 
diff --git a/src/util/src/tutil.c b/src/util/src/tutil.c
index 989273e0515e7c1affdd3ff9afe747688923270f..2392560370e97a21a191f1c1a3fb4bab986a65e9 100644
--- a/src/util/src/tutil.c
+++ b/src/util/src/tutil.c
@@ -447,10 +447,10 @@ int tasoUcs4Compare(void* f1_ucs4, void *f2_ucs4, int bytes) {
   int32_t ucs4_max_len = bytes + 4;
   char *f1_mbs = calloc(bytes, 1);
   char *f2_mbs = calloc(bytes, 1);
-  if (!taosUcs4ToMbs(f1_ucs4, ucs4_max_len, f1_mbs)) {
+  if (taosUcs4ToMbs(f1_ucs4, ucs4_max_len, f1_mbs) < 0) {
     return -1;
   }
-  if (!taosUcs4ToMbs(f2_ucs4, ucs4_max_len, f2_mbs)) {
+  if (taosUcs4ToMbs(f2_ucs4, ucs4_max_len, f2_mbs) < 0) {
     return -1;
   }
   int32_t ret = strcmp(f1_mbs, f2_mbs);
@@ -464,29 +464,29 @@ int tasoUcs4Compare(void* f1_ucs4, void *f2_ucs4, int bytes) {
 #endif
 }
 
-bool taosUcs4ToMbs(void *ucs4, int32_t ucs4_max_len, char *mbs) {
+int32_t taosUcs4ToMbs(void *ucs4, int32_t ucs4_max_len, char *mbs) {
 #ifdef USE_LIBICONV
   iconv_t cd = iconv_open(tsCharset, DEFAULT_UNICODE_ENCODEC);
   size_t ucs4_input_len = ucs4_max_len;
   size_t outLen = ucs4_max_len;
   if (iconv(cd, (char **)&ucs4, &ucs4_input_len, &mbs, &outLen) == -1) {
     iconv_close(cd);
-    return false;
+    return -1;
   }
   iconv_close(cd);
-  return true;
+  return (int32_t)(ucs4_max_len - outLen);
 #else
   mbstate_t state = {0};
   int32_t len = (int32_t) wcsnrtombs(NULL, (const wchar_t **) &ucs4, ucs4_max_len / 4, 0, &state);
   if (len < 0) {
-    return false;
+    return -1;
   }
   memset(&state, 0, sizeof(state));
   len = wcsnrtombs(mbs, (const wchar_t **) &ucs4, ucs4_max_len / 4, (size_t) len, &state);
   if (len < 0) {
-    return false;
+    return -1;
   }
-  return true;
+  return len;
 #endif
 }