diff --git a/src/plugins/http/src/gcJson.c b/src/plugins/http/src/gcJson.c
index 09990c123e6b3c0716bc38252689fbfa1ae46394..98069f434defbbda99399ee7ea4b773abc0a44b4 100644
--- a/src/plugins/http/src/gcJson.c
+++ b/src/plugins/http/src/gcJson.c
@@ -121,6 +121,7 @@ bool gcBuildQueryJson(HttpContext *pContext, HttpSqlCmd *cmd, TAOS_RES *result,
 
   for (int k = 0; k < numOfRows; ++k) {
     TAOS_ROW row = taos_fetch_row(result);
+    int32_t* length = taos_fetch_lengths(result);
 
     // for group by
     if (groupFields != -1) {
@@ -150,7 +151,11 @@ bool gcBuildQueryJson(HttpContext *pContext, HttpSqlCmd *cmd, TAOS_RES *result,
             break;
           case TSDB_DATA_TYPE_BINARY:
           case TSDB_DATA_TYPE_NCHAR:
-            len += snprintf(target + len, HTTP_GC_TARGET_SIZE - len, "%s:%s", fields[i].name, (char *)row[i]);
+            if (row[i]!= NULL){            
+              len += snprintf(target + len, HTTP_GC_TARGET_SIZE - len, "%s:", fields[i].name);
+              memcpy(target + len, (char *) row[i], length[i]);
+              len = strlen(target);
+            }
             break;
           default:
             len += snprintf(target + len, HTTP_GC_TARGET_SIZE - len, "%s:%s", fields[i].name, "-");