Discloses is a backlight module for providing a light beam to a liquid crystal panel, wherein, a set of optical film comprises a diffusion sheet for receiving the light beam from the light source; a prism sheet for receiving the light beam from the diffusion sheet and transferring the light beam to the liquid crystal panel, wherein, the prism sheet is close to the liquid crystal panel, and a plurality of protuberances with conical cross sections are provided on the surface of the prism sheet closing to the liquid crystal panel, and one part of the protuberances is provided with a plurality ofdefects. The scheme omits an upper diffusion sheet, can omit one step for the process flow, the manufacturing efficiency is greatly improved. In addition, the prism sheet can directly provide the backlight to the LCD panel, so that the backlight with better effects can be provided.