A light source module of a projector includes a beam splitter, a red light source, a blue light source, and a blue light source. The beam splitter has a first reflection side, on which a first splitter film is provided, and a second reflection side, on which a second splitter film is provided. An angle between a normal line of the first reflection side, and a normal line of the second reflection side, is in a range between 165 degrees and 180 degrees. Both the first splitter film and the second splitter film permit red rays to pass therethrough. The red light source is separated from the blue and green light sources to obtain a better thermal dissipation.