合并单元格的方法： 

sheet.addMergedRegion("起始行", "起始列", "终止行", "终止列");

合并示例：

//表头信息

HSSFRow row1= sheet.createRow(0);

cell = row1.createCell((short) 0);   

cell.setCellValue("");

sheet.addMergedRegion(new Region((short)0, (short) 0, (short)0, (short) 0));

cell = row1.createCell((short) 1); cell.setCellValue("时间");

sheet.addMergedRegion(new Region((short)0, (short) 1, (short)0, (short) 2));

 

HSSFRow row2= sheet.createRow(1);

cell = row2.createCell((short) 0);

cell.setCellValue("序号");

sheet.addMergedRegion(new Region((short)1, (short) 0, (short)1, (short) 0));

cell = row2.createCell((short) 1); cell.setCellValue("起始时间");

sheet.addMergedRegion(new Region((short)1, (short) 1, (short)1, (short) 1));

cell = row2.createCell((short) 2); cell.setCellValue("终止时间");

sheet.addMergedRegion(new Region((short)1, (short) 2, (short)1, (short) 2));

运行结果，得到的 Excel 表如下所示： 

文件样式可在导出后自行添加