System.IO.StringWriter sw = new System.IO.StringWriter();
sw.Write("<td style=\"width:40px; text-align:center; vertical align:middle;font-size:15px; font-weight: bold; height:49px;\">" + 0 + "</td>");
sw.Close();

Response.Clear();
Response.ContentEncoding = System.Text.Encoding.GetEncoding("GB2312");
Response.AddHeader("Content-Disposition", "attachment; filename=" + System.Web.HttpUtility.UrlEncode("测试", System.Text.Encoding.UTF8) + DateTime.Now.ToShortDateString() + ".xls");
Response.ContentType = "application/ms-excel";
Response.Write(sw);
Response.End();