An illumination system, adapted to provide an illumination beam, and comprising: an excitation light source, configured to emit an excitation beam; a wavelength conversion module, located on a transmission path of the excitation beam, and having at least one wavelength conversion region and a reflection region; a light splitting module located between the excitation light source and the wavelength conversion module, wherein the light splitting module has a transfer region and a light splitting region, and the excitation beam is incident to the wavelength conversion module through the transfer region, wherein when the at least one wavelength conversion region of the wavelength conversion module is cut into the transmission path of the excitation beam, the excitation beam is converted into at least one wavelength converted beam by the at least one wavelength conversion region of the wavelength conversion module, and when the reflection region of the wavelength conversion module is cut into the transmission path of the excitation beam, the excitation beam is reflected by the reflection region of the wavelength conversion module, and the excitation beam coming from the reflection region of the wavelength conversion module is split into a first sub-excitation beam and a second sub-excitation beam by the light splitting region of the light splitting module, wherein the first sub-excitation beam and the second sub-excitation beam form an excitation combination beam; and a light homogenizing element, located on a transmission path of the excitation combination beam and the at least one wavelength converted beam, and configured to uniform the excitation combination beam and the at least one wavelength converted beam; wherein a planar angle of the excitation combination beam incident to the light homogenizing element is larger than 0.25 times of a planar angle of the at least one wavelength converted beam incident to the light homogenizing element. an excitation light source, configured to emit an excitation beam; a wavelength conversion module, located on a transmission path of the excitation beam, and having at least one wavelength conversion region and a reflection region; a light splitting module located between the excitation light source and the wavelength conversion module, wherein the light splitting module has a transfer region and a light splitting region, and the excitation beam is incident to the wavelength conversion module through the transfer region, wherein when the at least one wavelength conversion region of the wavelength conversion module is cut into the transmission path of the excitation beam, the excitation beam is converted into at least one wavelength converted beam by the at least one wavelength conversion region of the wavelength conversion module, and when the reflection region of the wavelength conversion module is cut into the transmission path of the excitation beam, the excitation beam is reflected by the reflection region of the wavelength conversion module, and the excitation beam coming from the reflection region of the wavelength conversion module is split into a first sub-excitation beam and a second sub-excitation beam by the light splitting region of the light splitting module, wherein the first sub-excitation beam and the second sub-excitation beam form an excitation combination beam; and a light homogenizing element, located on a transmission path of the excitation combination beam and the at least one wavelength converted beam, and configured to uniform the excitation combination beam and the at least one wavelength converted beam; wherein a planar angle of the excitation combination beam incident to the light homogenizing element is larger than 0.25 times of a planar angle of the at least one wavelength converted beam incident to the light homogenizing element.