A diffusion plate and a backlight module for use in a liquid crystal display panel are provided. The backlight module includes a housing, a reflection plate, a light source, a diffusion plate and films. The diffusion plate has a plate body, a first supporter, and a second supporter. The plate body has a light exit surface. The first supporter and the second supporter are respectively disposed on two sides of the plate body and extend outwardly from the light exit surface. The films are disposed on the plate body and between the first and second supporters. The first and second supporters contact and support the liquid crystal display panel.