diff --git a/library/think/Model.php b/library/think/Model.php
index 55e7da8e..493d055a 100644
--- a/library/think/Model.php
+++ b/library/think/Model.php
@@ -958,14 +958,14 @@ abstract class Model implements \JsonSerializable, \ArrayAccess
             // 自动更新
             $this->autoCompleteData($this->update);
 
-            // 获取有更新的数据
-            $data = $this->getChangedData();
-
             // 事件回调
             if (false === $this->trigger('before_update', $this)) {
                 return false;
             }
 
+            // 获取有更新的数据
+            $data = $this->getChangedData();
+
             if (empty($data) || (count($data) == 1 && is_string($pk) && isset($data[$pk]))) {
                 // 关联更新
                 if (isset($relation)) {