The present disclosure provides a liquid crystal display and a backlight module thereof. The backlight module includes a light guide plate, a reflective layer, an optical film assembly and a light-emitting assembly. The optical film assembly is disposed on a top of the light guide plate, the reflective layer is disposed on a bottom of the light guide plate, the light-emitting assembly includes an LED light bar disposed opposite a light incident surface of the light guide plate and a substrate disposed on a bottom of the LED light bar, and the substrate extends to a bottom of the reflective layer. The present disclosure enlarges the assembly space of the substrate by disposing the substrate on the bottom of the reflective layer and extending the substrate to the bottom of the reflective layer, thereby making it easier to dissipate heat of the LED light bar.