Compared with intensity-modulated photon therapy, intensity-modulated proton therapy has significant dose advantages. However,the dose gradient of proton Bragg peak is relatively high,and the proton therapy is likely to be affected by range uncertainties,setup uncertainties and antonymic changes,etc. The difference between the planning dose and actual dose caused by respiratory motion hinders the widespread use of intensity-modulated proton therapy in thoracic cancers. In this paper,research progress on the effect of respiratory motion on intensity-modulated proton therapy and how to reduce the effect were summarized,aiming to provide reference for clinicians and researchers.