I tried to set Permissions on a folder by Computer Objects, i.e. Allows everyone to access that folder but denied some Computer from accessing that folder no matter who logined that computer. But the permission by computer entry never take effect when I test it. Anyone knows why? Thanks a lot!

Because it doesn't work the way you are thinking - it blocks the COMPUTER ACCOUNT for that computer from accessing the folder (really the LocalSystem account running under that computer's context), but not the user account on that machine.

AD doesn't work that way.

Maybe a firewall rule might help you there.

AD works more around users accounts then computer account, permissoning should be done via users accounts

Yes, can't restrict by Computers, finally, I used Group Policy to block exe files by Computers. Thanks!