diff --git a/chain.go b/chain.go
index 969a648..81c66d5 100644
--- a/chain.go
+++ b/chain.go
@@ -351,7 +351,10 @@ func (this *Query) QueryStmt() error {
 		return err
 	}
 	sql := helper.ToStr(res["sql"])
-	if this.conn == nil {
+
+	if SLAVER_DB != nil {
+		this.conn = SLAVER_DB
+	} else {
 		this.conn = DB
 	}