Abstract: A video system with a bi-directional transmission function is provided. The video system includes an video transmitter, a transmission interface and a video receiver. The video transmitter is coupled to the video receiver via the transmission interface (coaxial cable). The video transmitter is used for inserting a first control signal into the video signal according a synchronous signal of the video signal. The video transmitter is used for outputting the video signal with the first control signal to the video receiver via the transmission interface. The video receiver receives the video signal with the first control signal, and gets the first control signal from the video signal according to the synchronous signal of the video signal. In addition, the video receiver can insert a second control signal into the video signal and feedback the second control signal to the video transmitter via the transmission interface.