The present invention provides a backlight module comprises a waveguide, a reflector, and elastic members. Wherein the elastic members are used to arranged on corners of the waveguide, and the reflector is arranged on a side of the waveguide facing the elastic members. And wherein each of the elastic members is provided with a slot in a surface facing the reflector, and the reflector is provided with tabs corresponding to each of the slots so as to be securely received within the slots. The present invention further provides a liquid crystal display device incorporated with such a backlight module. By this arrangement, the backlight module become more reliable, and more suitable for narrow-boarder design. The utilization of the reflector is also enhanced.