A method for implementing Ring Back Tone (RBT) interworking, a Media Gateway Control Function (MGCF) device, and an Application Server (AS) are provided. A Multimedia Ring Back Tone (MRBT) service is triggered when a Circuit Switched (CS) user originates a call to an MRBT subscriber in an Internet Protocol Multimedia Subsystem (IMS). The method includes: receiving a message sent by an MRBT AS, where the message carries video RBT information; and notifying a Mobile Switching Center (MSC) to put through a calling terminal if determining that a video RBT needs to be played to the calling terminal according to the message. Therefore, a video RBT can be played when a CS user originates a call to an IMS user in the case of network interworking. An IMS video RBT may be played to the calling party when the CS user originates a call to the IMS user.