A multiple-layer optical film comprising: a transparent base layer, a diffusion layer formed on the base layer, and an upper prismatic layer formed on the diffusion layer having a plurality of root portions protruding downwardly from the upper prismatic layer to be respectively engaged with a plurality of recesses as recessed in the diffusion layer for firmly interlocking the upper prismatic layer with the diffusion layer. The diffusion layer includes nano or micron particles homogeneously dispersed in a resin matrix to obtain a composite layer having better light diffusibility; and the upper prismatic layer having nice light concentrating effect, thereby cooperatively synergetically forming a mul tiple-layer optical film having enhanced brightness, light uniformity, and dimensional stability.
