The invention discloses a cross-domain single-point registration system and method facing system integration. The system comprises a terminal, access proxy servers and a single-point registration server. Each access proxy server is disposed in front of a subsystem, positioned in the same top level domain with the subsystem, and used to process and forward all requests to the subsystem in full authority; and the single-point registration server comprises a unified registration interface, an authorization code generation module, an authorization code management module and a simulated registration module. Under the condition that codes of the system are not invaded and system setting is not changed, cross-domain cross-development-platform single-point registration is realized, and the system is suitable for a high concurrent scene and supports a registration-free condition. When a user access the subsystem, the corresponding access proxy server redirects a request to a unified registration interface, and a unique authorization code is generated after that the user succeeds in registration. A simulated registration manner is used to send the authorization code and registration information to the subsystem. The user can use the authorization code to access the system or other systems directly needless of registration again.