An optical diffusion module comprises a first diffusion structure comprising a plurality of convex portions and a plurality of concave portions arranged alternatingly, and a second diffusion structure comprising a plurality of convex portions and a plurality of concave portions arranged alternatingly. Light from a light source passes through the first diffusion structure and the second diffusion structure sequentially, and each convex portion is adjacent to a plurality of concave portions and each concave portion is adjacent to a plurality of convex portions, and the convex portions, the concave portions and each junction of the convex and concave portions have a curvature different from 0.