A backlight module has an upper frame and a lower frame engaged mutually for forming a receiving cavity therein, of which the upper frame has a stop base and is arranged at its top with a support sheet protruding inwardly along an inner perimeter thereof. A light-guide plate and a lighting member are arranged between the upper and lower frames, and a group of optical members is right on the support sheet in order to make the light from the lighting member via the light-guide platestop base uniform and to avoid the light being dissipated directly therefrom. Furthermore, the module is coupled with a substrate positioned on the stop base and over the optical members. The product thereby is easily and smoothly assembled. The group of optical members are conveniently checked, and the upper and lower frames are easily disassembled from each other if examination is necessary.