I find a way to solved this problem. But not the best way.
1,Boot from Knoppix CD with "knoppix 2".
2,Then copy the KNOPPIX files to your NFS directory: cp -Rp /KNOPPIX/* /mnt/hda1/cdrom
(if your hd-intalled the KNOPPIX on hda1)
3, reboot system without KNOPPIX CD
4, chroot /cdrom
5, remaster knoppix
6, Ctl+D return to hd-installed knoppix
7, edit /usr/share/knoppix-terminalserver/templates/miniroot/linuxrc, mount NFSDIR as /KNOPPIX, edit relation lines.
8, run knoppix-terminalserver
9, boot client
10, You will found it works great.
This way too waste hd space.
I'll find other way to solve this problem.