private void button4_Click(object sender, System.EventArgs e)
        {
            OleDbConnection cn = new OleDbConnection("Data Source=xsxxdb.mdb;Jet OLEDB:Engine Type=5;Provider=Microsoft.Jet.OLEDB.4.0");
            cn.Open();
            string sql = "select StudentInfo.StudentId as 自动编号,studentinfo.studentnumber as 学号,studentinfo.name as 姓名,studentinfo.sex as 性别,studentinfo.race as 族别,studentinfo.address as 家庭住址,studentinfo.telephone as 联系方式,studentinfo.role as 政治面貌,studentinfo.postalcode as 邮政编码,classinfo.classname as 班级名称,studentinfo.remark as 备注 from studentinfo inner join classinfo on studentinfo.classid = classinfo.classid where classinfo.classname='" + comboBox2.Text.ToString() + "' order by studentnumber";
            OleDbDataAdapter adp = new OleDbDataAdapter(sql, oleDbConnection1);
            DataSet ds = new DataSet();
            adp.Fill(ds, "student");
            AddExcel(ds);

        }

        protected void AddExcel(DataSet ds)
        {
            DataTable dt = ds.Tables["student"];
            string fileName = Guid.NewGuid() + ".xls";
            Excel.Application excel = new Excel.ApplicationClass();
            int rowIndex = 1;
            int colIndex = 0;
            excel.Application.Workbooks.Add(true);

            foreach (DataColumn col in dt.Columns)
            {
                colIndex++;
                excel.Cells[1, colIndex] = col.ColumnName;
            }
            foreach (DataRow row in dt.Rows)
            {
                rowIndex++;
                colIndex = 0;
                for (colIndex = 0; colIndex < dt.Columns.Count; colIndex++)
                {
                    excel.Cells[rowIndex, colIndex + 1] = row[colIndex].ToString();
                }
            }
            excel.Visible = true;
            excel.ActiveWorkbook.SaveAs(fileName, Excel.XlFileFormat.xlExcel9795, null, null, false, false, Excel.XlSaveAsAccessMode.xlNoChange, null, null, null, null, null);

            GC.Collect();
        }

将Excel采用模板式样，然后设置好文字的格式为字符

导入数据之前，先设置单元格格式