A method for establishing association-control relations includes these steps: An access adapting unit acquires subscription information of the user through a mobile application part (MAP) message, an SH interface message, or a Cx interface message; and acquires information indicating that the user is an ICS user from the subscription information of the user. A system, an access adapting unit, and an IMS CS control function (ICCF) for establishing association-control relations are also provided. In embodiments of the present invention, an access adapting unit such as a local-CS access adaptation function-network (L-CAAF-n) may know whether a user is an IMS centralized service (ICS) user and acquire the ICCF address information so that association-control relations may be established between the L-CAAF-n and the ICCF.