A problem for LDAP client configuration on CENT 6.0 X64
 

I have finished LDAP SERVER side,and it works.
but I found a problem on CLIENT side.
I can use both local account and LDAP account to log in my server.
how to set a priority to only allow LDAP auth if LDAP server is ok?

you really don't want to do this, it's so so not a good idea, and not even possible really, by design. Change your model instead. You shouldn't have two accounts with the same names, so there should never be a conflict, and you can never wholly remove local authentication as otherwise the root account would not work.