Provided are an image processing system and method thereof which communicates with an external image source device, the image processing system including: a display device which receives a modulated remote control signal modulated by a modulation method and demodulates the modulated remote control signal to generate a demodulated remote control signal and transmits the demodulated remote control signal; and a relay device which receives the demodulated remote control signal and modulates the demodulated remote control signal according to the modulation method to output an output remote control signal to the external image source device.