An illumination system comprising: an excitation light source, a first light splitting element, a first light reflecting element, a wavelength conversion device, and a light filtering device, wherein the excitation light source is adapted to provide an excitation beam, and the excitation beam comprises a first sub-beam and a second sub-beam; the first light splitting element is disposed on a transmission path of the excitation beam, and the first light splitting element comprises a first zone and a second zone; the first light reflecting element is disposed on a transmission path of the second sub-beam; the wavelength conversion device is disposed on a transmission path of the first sub-beam, and the wavelength conversion device comprises an optical zone and a wavelength conversion zone, wherein the wavelength conversion device is adapted to rotate around a central axis, such that the optical zone and the wavelength conversion zone alternately enter the transmission path of the first sub-beam, the wavelength conversion zone is adapted to convert the first sub-beam into a first conversion beam, and a wavelength of the first sub-beam is different from a wavelength of the first conversion beam; and the light filtering device is disposed on the transmission paths of the second sub-beam and the first conversion beam, wherein in a first time period, the optical zone of the wavelength conversion device enters the transmission path of the first sub-beam, the first sub-beam of the excitation beam is guided to the optical zone of the wavelength conversion device via the first zone of the first light splitting element, and meanwhile the second sub-beam of the excitation beam is guided to the light filtering device via the first light splitting element and the first light reflecting element and said second sub-beam is not guided to the optical zone of the wavelength conversion device, and in a second time period, the wavelength conversion zone enters the transmission path of the first sub-beam, and the first sub-beam is guided to the wavelength conversion zone of the wavelength conversion device to be converted into the first conversion beam. the excitation light source is adapted to provide an excitation beam, and the excitation beam comprises a first sub-beam and a second sub-beam; the first light splitting element is disposed on a transmission path of the excitation beam, and the first light splitting element comprises a first zone and a second zone; the first light reflecting element is disposed on a transmission path of the second sub-beam; the wavelength conversion device is disposed on a transmission path of the first sub-beam, and the wavelength conversion device comprises an optical zone and a wavelength conversion zone, wherein the wavelength conversion device is adapted to rotate around a central axis, such that the optical zone and the wavelength conversion zone alternately enter the transmission path of the first sub-beam, the wavelength conversion zone is adapted to convert the first sub-beam into a first conversion beam, and a wavelength of the first sub-beam is different from a wavelength of the first conversion beam; and the light filtering device is disposed on the transmission paths of the second sub-beam and the first conversion beam, wherein in a first time period, the optical zone of the wavelength conversion device enters the transmission path of the first sub-beam, the first sub-beam of the excitation beam is guided to the optical zone of the wavelength conversion device via the first zone of the first light splitting element, and meanwhile the second sub-beam of the excitation beam is guided to the light filtering device via the first light splitting element and the first light reflecting element and said second sub-beam is not guided to the optical zone of the wavelength conversion device, and in a second time period, the wavelength conversion zone enters the transmission path of the first sub-beam, and the first sub-beam is guided to the wavelength conversion zone of the wavelength conversion device to be converted into the first conversion beam.