diff --git a/src/tsdb/src/tsdbRead.c b/src/tsdb/src/tsdbRead.c
index 0bf533d027db284a12ae155dc494fd8f9f35a5f1..7b7c244ba8eb93730adc27714cb55b0ee75b6e35 100644
--- a/src/tsdb/src/tsdbRead.c
+++ b/src/tsdb/src/tsdbRead.c
@@ -1021,6 +1021,14 @@ static int32_t doLoadFileDataBlock(STsdbQueryHandle* pQueryHandle, SBlock* pBloc
 
   pBlock->numOfRows = pCols->numOfRows;
 
+  // Convert from TKEY to TSKEY for primary timestamp column if current block has timestamp before 1970-01-01T00:00:00Z
+  if(pBlock->keyFirst < 0 && colIds[0] == PRIMARYKEY_TIMESTAMP_COL_INDEX) {
+    int64_t* src = pCols->cols[0].pData;
+    for(int32_t i = 0; i < pBlock->numOfRows; ++i) {
+      src[i] = tdGetKey(src[i]);
+    }
+  }
+
   int64_t elapsedTime = (taosGetTimestampUs() - st);
   pQueryHandle->cost.blockLoadTime += elapsedTime;
 
@@ -1277,13 +1285,7 @@ int32_t doCopyRowsFromFileBlock(STsdbQueryHandle* pQueryHandle, int32_t capacity
     }
 
     if (pColInfo->info.colId == src->colId) {
-
-      if (pColInfo->info.type == TSDB_DATA_TYPE_TIMESTAMP) {
-        for (int32_t n = 0; n < num; n++) {
-          TKEY tkey = *(TKEY *)((char*)src->pData + bytes * start + n * sizeof(TKEY));
-          *(TSKEY *)(pData + n * sizeof(TSKEY)) = tdGetKey(tkey);
-        }
-      } else if (pColInfo->info.type != TSDB_DATA_TYPE_BINARY && pColInfo->info.type != TSDB_DATA_TYPE_NCHAR) {
+      if (pColInfo->info.type != TSDB_DATA_TYPE_BINARY && pColInfo->info.type != TSDB_DATA_TYPE_NCHAR) {
         memmove(pData, (char*)src->pData + bytes * start, bytes * num);
       } else {  // handle the var-string
         char* dst = pData;