An audio/video playback control system of liquid crystal display television (LCD TV) is provided to control an audio signal system, an image display system and a backlight source system of an LCD TV, and the control system uses an audio/video control unit to maintain an activated status in normal conditions, and the audio/video control unit receives a signal transmitted from an external control interface to determine whether or not to output an activate signal to activate the audio processing unit or activate the video processing unit and the backlight source system, or jointly activate the audio processing unit, the video processing unit and backlight source system, so as to achieve the digital control of the LCD TV and the power-saving purpose.