diff --git a/lib/xy.h b/lib/xy.h
index dd39274..9848aec 100644
--- a/lib/xy.h
+++ b/lib/xy.h
@@ -927,32 +927,31 @@ xy_normalize_path (const char *path)
     return new;
 }
 
+/**
+ * @note 总是返回不含末尾斜杠的父目录路径
+ */
 static char *
 xy_parent_dir (const char *path)
 {
   char *dir = xy_normalize_path (path);
+  dir = xy_str_gsub (dir, "\\", "/");
+  if (xy_str_end_with (dir, "/"))
+    dir = xy_str_delete_suffix (dir, "/");
+
   char *last = NULL;
+
+  last = strrchr (dir, '/');
+  if (!last)
+    {
+      /* current dir */
+      return ".";
+    }
+  *last = '\0';
+
   if (xy_on_windows)
-    {
-      last = strrchr (dir, '\\');
-      if (!last)
-        {
-          /* current dir */
-          return ".";
-        }
-      *last = '\0';
-    }
+    return xy_str_gsub (dir, "/", "\\");
   else
-    {
-      last = strrchr (dir, '/');
-      if (!last)
-        {
-          /* current dir */
-          return ".";
-        }
-      *last = '\0';
-    }
-  return dir;
+    return dir;
 }
 
 #endif