A bilayer photonic crystal photoswitch thin-film device having the optical characteristics of both 2D and 3D photonic crystals, and a preparation method thereof are provided. When the bilayer photonic crystal photoswitch thin-film device is rotated periodically, different colors can be observed at a fixed rotation angle, that is, the device has the attribute of changing colors by means of rotation, and can thus realize the opening and closing of an optical path. The bilayer photonic crystal photoswitch thin-film new device has broad application prospects in the fields of photoswitches, optical waveguides, optical prisms, warming signs, anti-counterfeiting and information coding, etc.