//源Execl名称
string sourceExeclFileName = "C:\\SourceExecl.xlsx";
//目标Execl名称
string targetExeclFileName = "C:\\TargetExecl.xlsx";
using (ExcelPackage package = new ExcelPackage(new FileInfo(targetExeclFileName)))
{
	using (ExcelPackage sourcePackage = new ExcelPackage(new FileInfo(sourceExeclFileName)))
	{
		//new sheet form copy为复制到目标Execl的SheetName
		package.Workbook.Worksheets.Add("new sheet from copy", sourcePackage.Workbook.Worksheets[1]);
	}
	package.Save();
}