With the development computer technology of campus network, more and more application systems become popular. These application systems are independent each other, everyone has its own different account information in different systems and must save its different account information. Based on the above fact, the paper analyzes common authentication scheme, then propose a security single sign-on way. The method implements a security uniform identity authentication using PKI,LDAP and CAS. In this way user can access all corresponding application systems when they login only one time.