I found the problem may be caused by altera_nios_dev_board_stratix_2s60_es.sof (under C:\altera\kits\nios2\components\altera_nios_dev_board_stratix_2s60_es\system)
When I upload the file named "vmlinux.bin", firstly, the above sof file will be downloaded to the board.
This time, I use the sof file for 2s60 (from example "hello world") instead of that one. No JTAG error appears. The sof file downloaded succusfully. Hence I think the most important thing is to find the right sof file for uCLinux to 2S60. Anyone have the project file or SOF file? I can rebuild it by myself. Or can send to me.
Regards
Yueran