An illumination system for a projector includes a light engine module, a light source module, a reflective mirror, a beam splitter, a phosphor wheel, and a lens assembly. The light source module can emit blue light along a first direction. The reflective mirror may reflect the blue light such that the blue light transmits in a second direction. A reflective region of the phosphor wheel can reflect a first portion of the blue light, and a first wavelength conversion region of the phosphor wheel can to activate a second portion of the blue light to form first band light. The lens assembly is configured to allow the first band light to pass through. The reflective region of the beam splitter is configured to reflect the first portion of the blue light and the first band light to the light engine module along the first direction.