diff --git a/src/Traits/GenUid.php b/src/Traits/GenUid.php
index 0f28da8..bb9c98b 100644
--- a/src/Traits/GenUid.php
+++ b/src/Traits/GenUid.php
@@ -13,7 +13,7 @@ protected static function boot()
         parent::boot();
         static::creating(function ($model) {
             if (empty($model->{$model->getKeyName()})) {
-                $model->{$model->getKeyName()} = uid();
+                $model->{$model->getKeyName()} = $this->uid();
             }
         });
     }
@@ -37,4 +37,14 @@ public function getKeyType()
     {
         return 'string';
     }
+
+    /**
+     * gen uid
+     * @param int $limit
+     * @return false|string
+     */
+    public function uid($limit = 9)
+    {
+        return substr(base_convert(sha1(uniqid(mt_rand())), 16, 36), 0, $limit);
+    }
 }