An optical film includes a first diffraction layer, a second diffraction layer, and a cover layer. The first diffraction layer includes a plurality of first diffraction gratings arranged in a direction on a surface thereof. The second diffraction layer is filled in the gap of the first diffraction gratings of the first diffraction layer and forms a plurality of second diffraction gratings arranged in a direction on the first diffraction layer, wherein the directions of the first diffraction gratings and the second diffraction gratings are parallel to each other. The cover layer fills and planarizes the second diffraction gratings of the second diffraction layer. The optical film can reduce the light leakage defect of a conventional liquid crystal display in a wide viewing angle and make the liquid crystal display have a uniform dark-state image and color image quality.