An ultra high definition display device and a video signal converting method are provided. The ultra high definition display device comprises a first input port configured to receive a first signal; a control module configured to generate a first enabling signal; a first receiver module configured to receive the first signal from the first input port according to the first enabling signal, and generate a second signal by a format conversion, both the first signal and the second signal being full high definition signals; a resolution transformation module configured to transform the second signal in resolution to generate a third signal, the third signal being an ultra high definition signal; and a transmission module configured to convert the third signal into an ultra high definition display signal and output the display signal. The device and method according to embodiments of the present invention may receive a full high definition signal, and achieve conversion from a full high definition signal to an ultra high definition signal display signal for output under the control of the control module.