问题已经得到解决
支付宝的 异步通知被 asp.net 的安全机制给拦截了 返回给支付宝的500错误信息是 A potentially dangerous Request.Form value was detected from the client 解决方法 : [HttpPost, ValidateInput(false)] public string notify(FormCollection collection) <httpRuntime requestValidationMode="2.0" />