The invention relates to a display signal extending apparatus and a method for transmitting the display signal. The display signal extending device is connected between a display signal source and a display for transmitting the display signal containing an audio and video signal and a display control signal. The display signal extending device comprises a transmission line, a differential signal output end, a differential signal receiving end, two signal conversion modules and two wireless signal transmission and receiving ends, wherein the differential signal output end is connected to the differential signal receiving end through a transmission line fro transmitting the audio and video signal. The two signal conversion modules are used for converting the display control signal and the wireless signal. The two wireless signal transmitting and receiving ends are respectively connected to the two signal conversion modules for transmitting and receiving the wireless signals.