An illumination system, comprising an excitation light source module, a light splitting and combining module, a filter module, and a wavelength conversion module, wherein the excitation light source module is configured to provide at least one excitation beam (EB1, EB2); the light splitting and combining module is disposed on a transmission path of the at least one excitation beam (EB1, EB2) from the excitation light source module, wherein the at least one excitation beam (EB1, EB2) from the light splitting and combining module comprises a first excitation beam and a second excitation beam, and the first excitation beam and the second excitation beam are different from each other in polarization state or wavelength range; the filter module is disposed on the transmission path of the at least one excitation beam (EB1, EB2) from the light splitting and combining module, wherein the filter module includes a light passing area configured to allow the at least one excitation beam (EB1, EB2) to pass there-through and at least one light filtering area configured to reflect the at least one excitation beam (EB1, EB2); and the wavelength conversion module is disposed on the transmission path of the at least one excitation beam (EB1, EB2) reflected by the at least one light filtering area, the wavelength conversion module is configured to convert the at least one excitation beam (EB1, EB2) reflected by the at least one light filtering area into a conversion beam and to reflect the conversion beam so that the conversion beam is transmitted toward the at least one light filtering area, and the at least one excitation beam (EB1, EB2) passing through the light passing area and the conversion beam passing through the at least one light filtering area form an illumination beam; wherein the illumination system further comprises a first lens module disposed on the transmission path of the at least one excitation beam (EB1, EB2) from the light splitting and combining module, and the first lens module is configured to focus the at least one excitation beam (EB1, EB2) from the light splitting and combining module on the filter module, wherein the first lens module has an optical axis; characterized in that the first excitation beam is incident to the filter module along a first direction, and the second excitation beam is incident to the filter module along a second direction, wherein the first direction and the second direction are located on two opposite sides of the optical axis of the first lens module. the light splitting and combining module is disposed on a transmission path of the at least one excitation beam (EB1, EB2) from the excitation light source module, wherein the at least one excitation beam (EB1, EB2) from the light splitting and combining module comprises a first excitation beam and a second excitation beam, and the first excitation beam and the second excitation beam are different from each other in polarization state or wavelength range; the filter module is disposed on the transmission path of the at least one excitation beam (EB1, EB2) from the light splitting and combining module, wherein the filter module includes a light passing area configured to allow the at least one excitation beam (EB1, EB2) to pass there-through and at least one light filtering area configured to reflect the at least one excitation beam (EB1, EB2); and the wavelength conversion module is disposed on the transmission path of the at least one excitation beam (EB1, EB2) reflected by the at least one light filtering area, the wavelength conversion module is configured to convert the at least one excitation beam (EB1, EB2) reflected by the at least one light filtering area into a conversion beam and to reflect the conversion beam so that the conversion beam is transmitted toward the at least one light filtering area, and the at least one excitation beam (EB1, EB2) passing through the light passing area and the conversion beam passing through the at least one light filtering area form an illumination beam; wherein the illumination system further comprises a first lens module disposed on the transmission path of the at least one excitation beam (EB1, EB2) from the light splitting and combining module, and the first lens module is configured to focus the at least one excitation beam (EB1, EB2) from the light splitting and combining module on the filter module, wherein the first lens module has an optical axis; characterized in that the first excitation beam is incident to the filter module along a first direction, and the second excitation beam is incident to the filter module along a second direction, wherein the first direction and the second direction are located on two opposite sides of the optical axis of the first lens module.