An optical lens includes a central optical portion and a mounting portion around the central optical portion. The central optical portion has a bottom and defines a central cavity recessed upwardly from the bottom. The central cavity is provided for receiving a light source therein. The bottom defines at least a frosted portion around the central cavity and at least a microstructure portion around the at least a frosted portion. A roughness of the at least a microstructure portion is larger than a roughness of the at least a frosted portion. The roughness of each of the at least a microstructure and frosted portion is gradually decreased alone a direction toward the central cavity.