A backlight module for providing a light with more uniform light distribution and greater brightness is provided. The backlight module includes at least a luminary for providing a light, a light guide assembly disposed adjacent to the luminary for guiding a first portion of the light, a translucent membrane with a plurality of openings thereon, and a reflector disposed below the light guide assembly. In which, a second portion of the light passes upwardly through the openings and a third portion of the light is directed upwardly by the light guide assembly after being reflected by the translucent membrane and the reflector. Further, the light guide assembly includes a plurality of light guide plates, in which the bottom of at least one light guide plate can be a triangular concave or an arc concave, and the light guide plates can have some doping particles therein.