I had download the doc-grub-20000128.tar.gz,then #make #/usr/src/mtd/util/doc_loadbios /dev/mtd0 grub_firmware and I found the partition I had make in /dev/nftla had lost,and fdisk /dev/nfla again make nfla1 mke2fs /dev/nfla1 then cp the root filesystem onto /dev/nfla1 reboot,system still boot my hda device.