The invention relates to a 2D YC separation device and YC separation system for separating a composite signal into a luma signal (Y) and a chroma signal (C). Firstly, the 2D YC separation device utilizes a low-pass filter to separate the composite signal into a low-frequency composite signal and a high-frequency composite signal. The low-frequency composite signal is a low-frequency luma signal. A 2D comb filter is utilized to separate the high-frequency composite signal into a high-frequency luma signal and the chroma signal. The luma signal is equal to the low-frequency luma signal plus the high-frequency luma signal. Therefore, the 2D YC separation device of the present invention can perfectly separate the composite signal so as to obtain a better luma signal and chroma signal. The YC separation system of the present invention further comprises a 3D YC separation device and a motion detection device, so as to obtain a precise luma signal and chroma signal.