diff --git a/src/plugins/monitor/src/monMain.c b/src/plugins/monitor/src/monMain.c
index a03bc09036d14045043704e82e22fdd177c243b2..1a1fc53740deb1e5e3a25645e55e519fb64be0b6 100644
--- a/src/plugins/monitor/src/monMain.c
+++ b/src/plugins/monitor/src/monMain.c
@@ -1239,41 +1239,41 @@ static void monSaveSlowQueryInfo() {
           monError("failed to save slow_query info, reason: invalid row %s len, sql:%s", (char *)row[i], tsMonitor.sql);
           goto DONE;
         }
-        pos += snprintf(sql + pos, strlen(SQL_STR_FMT) + charLen + 1, ", "SQL_STR_FMT, (char *)row[i]);
+        pos += snprintf(sql + pos, SQL_LENGTH - pos, ", "SQL_STR_FMT, (char *)row[i]);
       } else if (strcmp(fields[i].name, "user") == 0) {
         charLen = monGetRowElemCharLen(fields[i], (char *)row[i]);
         if (charLen < 0) {
           monError("failed to save slow_query info, reason: invalid row %s len, sql:%s", (char *)row[i], tsMonitor.sql);
           goto DONE;
         }
-        pos += snprintf(sql + pos, strlen(SQL_STR_FMT) + charLen + 1, ", "SQL_STR_FMT, (char *)row[i]);
+        pos += snprintf(sql + pos, SQL_LENGTH - pos, ", "SQL_STR_FMT, (char *)row[i]);
       } else if (strcmp(fields[i].name, "qid") == 0) {
         charLen = monGetRowElemCharLen(fields[i], (char *)row[i]);
         if (charLen < 0) {
           monError("failed to save slow_query info, reason: invalid row %s len, sql:%s", (char *)row[i], tsMonitor.sql);
           goto DONE;
         }
-        pos += snprintf(sql + pos, strlen(SQL_STR_FMT) + charLen + 1, ", "SQL_STR_FMT, (char *)row[i]);
+        pos += snprintf(sql + pos, SQL_LENGTH - pos, ", "SQL_STR_FMT, (char *)row[i]);
       } else if (strcmp(fields[i].name, "created_time") == 0) {
         int64_t create_time = *(int64_t *)row[i];
         create_time = convertTimePrecision(create_time, TSDB_TIME_PRECISION_MILLI, TSDB_TIME_PRECISION_MICRO);
-        pos += snprintf(sql + pos, SQL_LENGTH, ", %" PRId64 "", create_time);
+        pos += snprintf(sql + pos, SQL_LENGTH - pos, ", %" PRId64 "", create_time);
       } else if (strcmp(fields[i].name, "time") == 0) {
-        pos += snprintf(sql + pos, SQL_LENGTH, ", %" PRId64 "", *(int64_t *)row[i]);
+        pos += snprintf(sql + pos, SQL_LENGTH - pos, ", %" PRId64 "", *(int64_t *)row[i]);
       } else if (strcmp(fields[i].name, "ep") == 0) {
         charLen = monGetRowElemCharLen(fields[i], (char *)row[i]);
         if (charLen < 0) {
           monError("failed to save slow_query info, reason: invalid row %s len, sql:%s", (char *)row[i], tsMonitor.sql);
           goto DONE;
         }
-        pos += snprintf(sql + pos, strlen(SQL_STR_FMT) + charLen + 1, ", "SQL_STR_FMT, (char *)row[i]);
+        pos += snprintf(sql + pos, SQL_LENGTH - pos, ", "SQL_STR_FMT, (char *)row[i]);
       } else if (strcmp(fields[i].name, "sql") == 0) {
         charLen = monGetRowElemCharLen(fields[i], (char *)row[i]);
         if (charLen < 0) {
           monError("failed to save slow_query info, reason: invalid row %s len, sql:%s", (char *)row[i], tsMonitor.sql);
           goto DONE;
         }
-        pos += snprintf(sql + pos, strlen(SQL_STR_FMT) + charLen + 2, ", "SQL_STR_FMT")", (char *)row[i]);
+        pos += snprintf(sql + pos, SQL_LENGTH - pos, ", "SQL_STR_FMT")", (char *)row[i]);
       }
     }
   }