diff --git a/library/think/db/Builder.php b/library/think/db/Builder.php
index e80a2fb7..6c19ada0 100644
--- a/library/think/db/Builder.php
+++ b/library/think/db/Builder.php
@@ -660,12 +660,16 @@ abstract class Builder
     /**
      * 设置锁机制
      * @access protected
-     * @param bool $lock
+     * @param bool|string $lock
      * @return string
      */
     protected function parseLock($lock = false)
     {
-        return $lock ? ' FOR UPDATE ' : '';
+        if (is_bool($lock)) {
+            return $lock ? ' FOR UPDATE ' : '';
+        } elseif (is_string($lock)) {
+            return ' ' . trim($lock) . ' ';
+        }
     }
 
     /**
diff --git a/library/think/db/Query.php b/library/think/db/Query.php
index ceb3d500..e7f735ea 100644
--- a/library/think/db/Query.php
+++ b/library/think/db/Query.php
@@ -1493,7 +1493,7 @@ class Query
     /**
      * 指定查询lock
      * @access public
-     * @param boolean $lock 是否lock
+     * @param bool|string $lock 是否lock
      * @return $this
      */
     public function lock($lock = false)