Method for switching video receiving interface and circuit system

A method for switching audio-visual interfaces and a circuit system are provided. The circuit system is disposed in a sink device. A protocol layer circuit of each of audio-visual interfaces in the sink device includes a status and control data channel control module, which is used to respond to the signals sent by the video sources continuously when the sink device is connected with audio-visual sources via the audio-visual interfaces. The multiple video sources can accordingly send FRL (fixed rate link) signals to the sink device in response to responses made by the sink device. The protocol layer circuit includes an FRL audio-visual packet detection module that starts to detect a rate of an FRL and resolve audio-visual packets for obtaining audio-visual data for the audio-visual interface that the sink device switches to.