Embodiments of the present invention disclose a method, an apparatus, and a system for service control via an I1 interface. The method includes: sending a Session Initiation Protocol Invite message to a user equipment through a Gm interface; if receiving a response message returned by the user equipment, where the response message indicates that the user equipment chooses to use a circuit switched bearer and use an I1 interface for control, sending an I1 Invite message to the user equipment through the I1 interface, where I1 Invite message carries information indicating that Gm interface control falls back to the I1 interface control and information used to associate the Session Initiation Protocol Invite message.