The invention provides an optical film, a backlight module comprising the same and a display device. The optical film comprises a polarizing film and a diffusing film, wherein the polarizing film is used for converting incident light into polarized light and then emitting the polarized light; the diffusing film is arranged on the emergent surface of the polarizing film, and comprises scattering particles capable of forming Rayleigh scattering. The backlight module comprises an optical film and a light source; the light source is arranged on one side, away from the diffusing film, of the polarizing film. According to the optical film provided by the invention, the problems that the conventional diffusing film cannot be thinned, has a poor light uniformizing effect and causes brightness lossare solved; the polarizing film can convert the incident light into the polarized light and then emit the polarized light, so that the light coming into the diffusing film is the polarized light; thescattering particles in the diffusing film can diffuse the polarized light emitted from the polarizing film, so that the light uniformizing effect is enhanced and the brightness after diffusion is enhanced; the optical film is small in thickness; the backlight module facilitates reduction in the light mixing distance; the light uniformizing effect is enhanced; the overall brightness of the moduleis improved; thinning of a product is facilitated.