when i first login Integrityserver ,what is the default username/password?

If you are using the "MKSdomain" authentication and not LDAP, there is a file in <server install directory>/data called "password.properties".

In that file you can set up the usernames and passwords and it should load those usernames the next time the server restarts.

You can read more about this in the "Server Installation and Configuration Guide" pdf under the server security section.