I am confusing with TcpMaxDataRetransmissions parameter in windows.
Accounding to this page, TcpMaxDataRetransmissions means that the times that windows will retransmit for an un-acked packet.
The default value in windows 2003 is 5.
But Why I see 8 retransmission times in a wireshark sniffer file?

The problem solved, 5 works. Windows server retransmission one packet at most 5 times by default.
Note the pmtu(len 524 packets), do not include that ‘five times’