A backlight module is disclosed. The backlight module includes a light guide plate, a light source, a back plate, and a positioning component for maintaining a light coupling distance between the light emitting surface of the light source and the light incident surface of the light guide plate. There is a light coupling distance between the light emitting surface of the light source and the light incident surface of the light guide plate. When a temperature change occurs, the positioning component occurs as a first deformation, as well as the light guide plate occurs as a second deformation. The light coupling distance remains unchanged under the influence of the first deformation and the second deformation. The positioning reliability of the light guide plate is improved in the present invention.