The present invention provides a LCD device, and its backlight module and back plate assembly. The back plate assembly contains a back plate, a blocking rim, a side wall, and a buffering element. The back plate supports the optical member of the backlight module. The blocking rim fixes the optical member jointly with the back plate, and supports a liquid crystal panel. The side wall has a back edge connected with the back plate and a front edge connected with the blocking rim. The buffering element is configured at an edge of the blocking rim that is away from the side wall and attached to the optical member and a liquid crystal panel, respectively. The present invention prevents the optical member and liquid crystal panel from contacting with the blocking rim and thereby being scratched, so as to provide effective protection.