Aiming at the problem of low efficiency and poor system security due to the multiple authentication of users under multiple application systems, we propose a cookie-based cross-domain single sign-on scheme. Users can login once but access multiple systems in different domains. We provide the overall model of the scheme, analyze the login process and explain the implementation of the cross-domain. The mutual authentication is explained in details, which ensures the legitimate identity of both sides of communication. The management of role-identity is added to reduce the coupling between single sign-on systems and web application systems.