diff --git a/library/think/db/Query.php b/library/think/db/Query.php
index 049afea4..120ef9e5 100644
--- a/library/think/db/Query.php
+++ b/library/think/db/Query.php
@@ -595,8 +595,9 @@ class Query
             if (false === $step) {
                 return true; // 等待下次写入
             }
+            $step = -$step;
         }
-        return $this->setField($field, ['exp', $field . '+' . $step]);
+        return $this->setField($field, ['exp', $field . '-' . $step]);
     }
 
     /**