protected void Button1_Click(object sender, EventArgs e)
    {
        Export("application/ms-excel", "学生成绩报表.xls");
    }
    private void Export(string FileType, string FileName)
    {
        Response.Charset = "GB2312";
        Response.ContentEncoding = System.Text.Encoding.UTF7;
        Response.AppendHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(FileName, Encoding.UTF8).ToString());
        Response.ContentType = FileType;
        this.EnableViewState = false;
        StringWriter tw = new StringWriter();
        HtmlTextWriter hw = new HtmlTextWriter(tw);
        GridView1.RenderControl(hw);
        Response.Write(tw.ToString());
        Response.End();
    }

在GridView1.RenderControl(hw);写入前对它进行重新绑定，绑定你要导出的数据.