An illumination system, comprising: a light source device , a light homogenizing element , and a polarization element , wherein the light source device comprises a first laser light source , a second laser light source , a third laser light source and a first compensation laser light source , the first laser light source is configured to provide a first beam (L1), the second laser light source is configured to provide a second beam (L2), the third laser light source is configured to provide a third beam (L3), and the first compensation laser light source is configured to provide a first compensation beam (L4), the first compensation beam (L4) is a red light, wherein polarization states of the first beam (L1) and the first compensation beam (L4) are the same, and polarization states of the second beam (L2) and the third beam (L3) are the same and different from polarization states of the first beam (L1) and the first compensation beam (L4); the light homogenizing element is disposed on transmission paths of the first beam (L1), the second beam (L2), the third beam (L3), and the first compensation beam (L4) and is configured to convert the first beam (L1), the second beam (L2), the third beam (L3), and the first compensation beam (L4) into an illumination beam (LB); the polarization element is disposed on the transmission paths of the first beam (L1) and the first compensation beam (L4) and is located between the light source device and the light homogenizing element , and the first beam (L1) and the first compensation beam (L4) pass through the polarization element to change polarization states of the first beam (L1) and the first compensation beam (L4) to be the same as polarization states of the second beam (L2) and the third beam (L3). wherein the light source device comprises a first laser light source , a second laser light source , a third laser light source and a first compensation laser light source , the first laser light source is configured to provide a first beam (L1), the second laser light source is configured to provide a second beam (L2), the third laser light source is configured to provide a third beam (L3), and the first compensation laser light source is configured to provide a first compensation beam (L4), the first compensation beam (L4) is a red light, wherein polarization states of the first beam (L1) and the first compensation beam (L4) are the same, and polarization states of the second beam (L2) and the third beam (L3) are the same and different from polarization states of the first beam (L1) and the first compensation beam (L4); the light homogenizing element is disposed on transmission paths of the first beam (L1), the second beam (L2), the third beam (L3), and the first compensation beam (L4) and is configured to convert the first beam (L1), the second beam (L2), the third beam (L3), and the first compensation beam (L4) into an illumination beam (LB); the polarization element is disposed on the transmission paths of the first beam (L1) and the first compensation beam (L4) and is located between the light source device and the light homogenizing element , and the first beam (L1) and the first compensation beam (L4) pass through the polarization element to change polarization states of the first beam (L1) and the first compensation beam (L4) to be the same as polarization states of the second beam (L2) and the third beam (L3). <EOS>