谢谢，根据你提供的代码，我自己修改成功了，把Textbox控件里的数据成功导入Excel，代码如下：

private void button2_Click(object sender, EventArgs e)
        {
            SaveFileDialog sfd = new SaveFileDialog();
            sfd.DefaultExt = "xls";    //设置默认扩展名为xls
            sfd.Filter = "Excel文件(*.xls)|*.xls";//另存文件时文件类型框中出现的内容
            if (sfd.ShowDialog() == DialogResult.OK)  //获取选定的另存文件对话框存在
            {
                DoExport(this.textBox2, sfd.FileName);
            }
        }
        private void DoExport(TextBox textbox, string strFileName)
        {
           // string[] lines = System.Text.RegularExpressions.Regex.Split(textbox.Text, "/r/n");
          //  int rowNum = lines.Length;//获取 TextBox2控件里的数据行数
            int rowNum=textbox.Lines.Length; //读取Textbox控件里数据的行数
            int rowIndex = 1;   //定义一个Excel行
            int col = 1;        //定义一个Excel列，默认为1
            if (rowNum == 0 || string.IsNullOrEmpty(strFileName)) //控件里没有数据
            {
                return;
            }
            if (rowNum > 0)//控件里有数据
            {
                Microsoft.Office.Interop.Excel.Application xlApp = new Microsoft.Office.Interop.Excel.ApplicationClass();
                if (xlApp == null)
                {
                    MessageBox.Show("无法创建Excel对象，可能您的系统未安装Excel");
                    return;
                }
                xlApp.DefaultFilePath = "";
                xlApp.DisplayAlerts = true;
                xlApp.SheetsInNewWorkbook = 1;
                Microsoft.Office.Interop.Excel.Workbook xlBook = xlApp.Workbooks.Add(true);
                for (int i = 0; i < rowNum; i++)//将数据导入Excel
                {
                    string ss = textbox.Lines[i].ToString();  //读取相对应行的数据，这里只是测试用
                    rowIndex++;
                    xlApp.Cells[rowIndex,col] = Convert.ToString(textbox.Lines[i].ToString()) + "\t";//读取到的Textbox控件里的数据导入到Excel
                    //xlApp.Rows[rowIndex,0] = Convert.ToString(textbox.Lines[i].ToString()) + "\t";
                }
                xlBook.SaveAs(strFileName, Microsoft.Office.Interop.Excel.XlFileFormat.xlWorkbookNormal, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Microsoft.Office.Interop.Excel.XlSaveAsAccessMode.xlExclusive, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);
                xlApp = null;
                xlBook = null;
                MessageBox.Show("数据导入成功！！");
            }
           

        }