A communication system and method thereof are provided, which includes: providing a first mask, a second mask, a user device having a screen and a display device having a light code module and a panel, wherein the first mask and the second mask are positioned at different positions of the panel, respectively; providing a light code signal to the panel by the light code module, and providing a first mask signal and a second mask signal by the first mask and the second mask, respectively; and capturing the light code signal plus the first mask signal or the second mask signal from the panel by the user device to obtain a first code according to the combination of the light code signal and the first mask signal or obtain a second code according to the combination of the light code signal and the second mask signal.