A light source module includes a light source and an optical lens facing the light source. The optical lens includes a light incident face facing the light source, a light emitting face opposite to the light incident face, and a connecting face connecting the light incident face and the light emitting face. The connecting face is planar. The light emitting face includes a lateral face extending upwardly from an outer periphery of the connecting face and a top face located above the light incident face. The optical lens further includes a plurality of protrusions protruding outwardly from the light emitting face, and a plurality of grooves defining in the connecting face. The protrusions are formed on the lateral face and located adjacent to the connecting face, and the grooves are located adjacent to the lateral face.