diff --git a/library/think/Model.php b/library/think/Model.php
index 94b61bac..019cb8dc 100644
--- a/library/think/Model.php
+++ b/library/think/Model.php
@@ -1161,16 +1161,8 @@ abstract class Model implements \JsonSerializable, \ArrayAccess
      */
     public function setInc($field, $step = 1, $lazyTime = 0)
     {
-        // 删除条件
-        $pk = $this->getPk();
-
-        if (is_string($pk) && isset($this->data[$pk])) {
-            $where = [$pk => $this->data[$pk]];
-        } elseif (!empty($this->updateWhere)) {
-            $where = $this->updateWhere;
-        } else {
-            $where = null;
-        }
+        // 更新条件
+        $where = $this->getWhere();
 
         $result = $this->getQuery()->where($where)->setInc($field, $step, $lazyTime);
         if (true !== $result) {
@@ -1190,6 +1182,23 @@ abstract class Model implements \JsonSerializable, \ArrayAccess
      * @throws Exception
      */
     public function setDec($field, $step = 1, $lazyTime = 0)
+    {
+        // 更新条件
+        $where  = $this->getWhere();
+        $result = $this->getQuery()->where($where)->setDec($field, $step, $lazyTime);
+        if (true !== $result) {
+            $this->data[$field] -= $step;
+        }
+
+        return $result;
+    }
+
+    /**
+     * 获取更新条件
+     * @access protected
+     * @return mixed
+     */
+    protected function getWhere()
     {
         // 删除条件
         $pk = $this->getPk();
@@ -1201,13 +1210,7 @@ abstract class Model implements \JsonSerializable, \ArrayAccess
         } else {
             $where = null;
         }
-
-        $result = $this->getQuery()->where($where)->setDec($field, $step, $lazyTime);
-        if (true !== $result) {
-            $this->data[$field] -= $step;
-        }
-
-        return $result;
+        return $where;
     }
 
     /**
@@ -1335,14 +1338,7 @@ abstract class Model implements \JsonSerializable, \ArrayAccess
         }
 
         // 删除条件
-        $pk = $this->getPk();
-        if (is_string($pk) && isset($this->data[$pk])) {
-            $where = [$pk => $this->data[$pk]];
-        } elseif (!empty($this->updateWhere)) {
-            $where = $this->updateWhere;
-        } else {
-            $where = null;
-        }
+        $where = $this->getWhere();
 
         // 删除当前模型数据
         $result = $this->getQuery()->where($where)->delete();