A projector is provided, which includes a red substrate, a green substrate, a blue substrate, an X-cube, an electronic control element, a light guide element, a light valve element, and a projection lens. The red substrate, the green substrate, and the blue substrate respectively illuminate three surfaces of the X-cube, and the light is mixed in the X-cube and then exits from a light emitting surface. The electronic control element controls the red substrate, the green substrate, and the blue substrate. The light guide element is used for reflecting the light from the light emitting surface of the X-cube. The light valve element is used for reflecting the light from the light guide element back to the light guide element, and the light passes through the light guide element and then projected by the projection lens onto a projection plane area. Thereby, the ON/OFF switch time of the present invention is shortened, the temperature may not get over high, the optical efficiency is enhanced, and the whole volume is significantly reduced.