A backlight unit for enhancing brightness of a TFT-LCD device is disclosed. The backlight unit comprises a plurality of lamp tubes, a diffuser plate and a reflector. The lamp tubes are disposed in the space encompassed by the diffuser plate and the reflector and are arranged with a selected interval. The diffuser plate is disposed above the lamp tubes for passing and diffusing the light emitted from said lamp tubes. The reflector plate is disposed beneath said lamp tubes for reflecting the light emitted from said lamp tubes back to said diffuser plate. The reflector plate has a plurality of particles fabricated thereon for scattering the reflected light uniformly.