A system and apparatus for providing services are provided by embodiments of the present invention. It is guaranteed that a UE is able to establish a call branch at the CS network side with a CSA. The CSA and the S-CSCF are able to establish a call branch at an IMS network side between the CSA and the S-CSCF for the UE. Embodiments of the present invention further provide a method for providing services. The method includes: registering a UE in a Circuit Switched, CS, network, registering the UE in an IP Multimedia Sub-system, IMS, network and establishing a call branch at the CS network side between the UE and the IMS network for an IMS session, wherein registering the UE in the IMS network comprises registering CS access capability of the UE in the IMS network. The system, apparatus and method provided by embodiments of the present invention for providing services may support a UE to access an IMS service platform via a CS network, which effectively reduces the cost.