The invention belongs to the technical field of optical thin films and particularly relates to a color separation component through transmission of a visible light band (0.6-0.9 [mu]m), a laser band (1.06 [mu]m) and a middle infrared band (3.0-5.0 [mu]m) and a design method. In the color separation component, two parallel plate optical components with the working angle of 45 degrees are adopted, and colors are separated according to an infrared band transmission method, a visible light band reflection method and a laser transmission method sequentially through reasonable selection of optical thin films on the two sides of each of the plate optical components; the average light splitting coefficient of the middle infrared band is 96% or higher, the average light splitting coefficient of the visible light band is 98% or higher, and the average light splitting coefficient of the laser band (1.06 [mu]m) is 98% or higher.