diff --git a/lib/user.js b/lib/user.js
index ad295f42..fb851b1e 100644
--- a/lib/user.js
+++ b/lib/user.js
@@ -275,7 +275,7 @@ Volcanos("user", {help: "用户操作", info: {}, agent: {
 		}
 		can.page.ClassList.add(can, ui._target, chat.FLOAT)
 		if (layout.top) {
-			can.page.style(can, ui.content, html.MAX_HEIGHT, window.innerHeight - layout.top - 200)
+			can.page.style(can, ui.content, html.MAX_HEIGHT, window.innerHeight - layout.top - html.ACTION_HEIGHT - 10)
 		}
 
 		var action = can.onappend._action(can, button||[html.SUBMIT, html.CANCEL], ui.action, {