>CreateFile control Serial Port,dwFlagsAndAttributes must set FILE_FLAG_OVERLAPPED,if use FILE_FLAG_OVERLAPPED in CreateFile,How to use WriteFile lpOverlapped.

I can't test this code. Here is the link that shows how to use lpOverlapped
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnfiles/html/msdn_serial.asp

The OVERLAPPED structure:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dllproc/base/overlapped_str.asp