Traditional Single Sign-On solution is not suitable for the heterogeneous applications since it’s generally for web portals and other distributed web applications, there isn’t a suitable solution for the disparate applications in which both C/S and B/S mode exist, and whose server sides are not allowed to modify. This paper introduces the characteristic of the traditional single sign-on solution CAS, combines it with the assistant technology in B/S and C/S mode that are Windows message mechanism and browser plug-in technology, then proposes a new sign-on model for heterogeneous applications that is based on assistant technology and authentication data centralized managed.