The invention provides a backlight module, including: an optical plate and an optical film, wherein at least one edge of optical film being disposed with a protruding ear, protruding ear having a via hole; backlight module further comprising at least a hanging element; wherein a side of the optical plate corresponding to edge of optical film with protruding ear being fixedly connected to hanging element; optical film being disposed on top of optical plate and via hole hanging on hanging element so as to fasten optical film. The backlight module improves the fix reliability of optical plate and prevents from arching up caused by thermal expansion. Because optical plate and optical film expand simultaneously due to heat, the wavy curve of the optical film is avoided and optical quality is improved. The present invention also discloses a liquid crystal display device with the backlight module.