The invention relates to a receiving device for an audio-video system. The receiving device comprises a connector, a video processing unit, an audio processing module, and a monitoring unit. The monitoring unit detects a status of an inputted signal received by the connector and controls the operation of at lease one of the video processing unit and the audio processing module in accordance with the detected result to avoid the audio-video system display abnormal image or play noise when the receiving device did not receive the inputted signal by accident.