An illumination system includes a beam splitting unit, a first lamp, a second lamp and a reflective component. The beam splitting unit has a splitting interface. One of the first lamp, the second lamp and the reflective component is disposed at one side of the beam splitting interface, and the others are disposed at the other side of the splitting interface. Moreover, a first beam and a second beam are respectively provided by the first lamp and the second lamp. The beam splitting unit is adapted to pass through a portion of the first beam and the second beam and reflect the other portion of the first beam and the second beam. The reflective component, the first lamp and the second lamp are adapted to reflect the collected portions of the first beam and the second beam back to the beam splitting unit.