An optical film capable of delivering high level of brightness including a surface of an incident plane of the optical film constructed with multiple light penetration areas segregated by multiple reflection microstructures each provided with a groove; each groove is covered up with a reflective material; and when the optical film is applied in a backlight module, all streams of light entering into the optical film are effectively centered on those light penetration areas constructed on the optical film for further irradiation out of the optical film.