A light source module is provided. The light source module includes a reflector, a light source, a transparent cover, a fluorescent material layer, and an optical lens. The light source is disposed inside the reflector, and the light source is suitable for emitting light including white light. The light source is enveloped with the transparent cover and the reflector. The fluorescent material layer is disposed on the transparent cover and the light emitted from the light source is suitable for exciting the fluorescent material layer to emit red light. The optical lens is disposed on an optical path of the light source, and the transparent cover is located between the optical lens and the light source. By utilizing the aforementioned structures, the intensity of the red light can be increased. Moreover, an optical projection system is also provided.