A liquid crystal display and the backlight module thereof are disclosed. The backlight module includes a substrate, a light guiding plate, a first pillar, a light source, at least two separating pieces, and an elastic piece. The separating pieces keep the distance between the light guiding plate and the lighting assembly of the light source equals to a minimum distance. A first end of the elastic piece connects one end of the first pillar passing through the crack of the substrate, and a second end of the elastic piece connects to the substrate. The elastic piece pushes the light guiding plate via the first pillar to move toward the light source until the distance between the light guiding plate and the lighting assembly of the light source equals to the minimum distance. The liquid crystal device and the backlight module are capable of keeping the coupling distance of the backlight module remain unchanged.