diff --git a/Apps/Explorer/desk_server.vp b/Apps/Explorer/desk_server.vp
index 7fae84b..51a12e3 100644
--- a/Apps/Explorer/desk_server.vp
+++ b/Apps/Explorer/desk_server.vp
@@ -1371,7 +1371,9 @@ class DeskServer:
                 viperlib.snprintf(&_fb1, 128, "[explorer] first FLUSH win=%d uy=%d h=%d\n", win, s.uy, s.h)
                 devfs.serial_puts(&_fb1)
             _flush_cnt += 1
-            self.mark(s.uy, s.h)
+            # 最小化窗口仍在后台绘制/FLUSH：不要置脏，否则合成器每帧都要重画背景。
+            if s.minimized == 0:
+                self.mark(s.uy, s.h)
         elif ty == uint32(desk.DESK_REQ_ACTIVATE):
             self.next_z += 1
             s.z_order = self.next_z