The present application discloses a liquid crystal display device and a backlight module thereof. The backlight module comprises a backboard, a separating plate, and a light source component; wherein the backboard has a base plate and a plurality of side plates, and the backboard is an injection molding board; the separating plate is mounted in an accommodating groove, a heat dissipation chamber is formed between the separating plate and the base plate, in the heat dissipation chamber, the backboard is provided with convection holes; the light source component comprises a plurality of lamp substrates and a plurality of LED lamps mounted on the lamp substrates, the lamp substrates are located within the heat dissipation chamber, and the separating plate is provided with transparent holes enabling light emitted by each of the LED lamps to penetrate the separating plate in a thickness direction of the separating plate.