An illumination system includes a light source module, a light splitting module, a light consolidating module and a waveband converting module. The light source module has a first light source, which provides a first light beam of first waveband. The light splitting module has a first light splitting element and a second light splitting element. The first light splitting element allows the light beam of first waveband to pass through and reflects the light beam of second waveband. The second light splitting element allows the light beam of second waveband to pass through and reflects the light beam of first waveband. The light consolidating module reflects the light beam having an incident angle greater than a predetermined angel and allows the light beam having an incident angle smaller than the predetermined angel to pass through. The waveband converting module has a first waveband converting zone.