Hi rayzhahng,
We regret for the delay in getting back to you.
please refer the following code to display headers in the excel worksheet after exporting to excel
sheet.UsedRange.MoveTo(sheet[row, column, lastRow, lastCol]);
sheet.UsedRange["A3:D3"].Merge(true);
sheet.UsedRange["A3:D3"].Text = "This is Description";
Sample for reference
http://www.syncfusion.com/uploads/redirect.aspx?&team=support&file=GCExportWithHeaderSheetshow-1881380379.zipRegards,
Kalai