A back plate assembly includes a heat dissipating member and a back cover. The heat dissipating member includes a base plate for mounting a light guide plate and a side plate for mounting a LED light source. The base plate extends along a first direction, and includes a first surface facing a display and a second surface opposite to the first surface. The side plate is connected to the base plate, and extends along a second direction perpendicular to the first direction. The back cover is disposed on the base plate and is made of plastic material. The back cover includes a third surface facing the display and coplanar with or higher than the first surface. With the present disclosure, the manufacturing cost of the light guide plate is reduced and no complicated fixing structures are required to fix the light guide plate on the back plate.