Abstract: Tumor radiotherapy increases radiation dose in a tumor target area and improves protection for normal tissues and organs around tumors. Proton beam therapy (PBT) is the most advanced radiotherapy technology worldwide. In theory, the unique Bragg peak and superior relative biological effect of proton beam can deliver a maximum dose to tumor target areas, reduce the dose received by normal tissues and organs around tumors, achieve the "directional blasting" of a tumor target area, and improve the local treatment and control rates of tumors. This method has better features than traditional photon therapy. Currently, existing clinical studies focus on melanoma; lung, esophageal, breast, liver, and prostate cancers; childhood malignant tumor; and other diseases. However, most of these studies are retrospective clinical studies, and the cost of establishing and maintaining a proton equipment is immense. Thus, proton therapy for malignant tumors remains controversial. Future studies must address the insufficient clinical evidence of PBT, and biological effects are still under investigation. Overcoming these deficiencies is associated with the rapid development of PBT. This review discusses the physical and biological characteristics of PBT, and its application in cancer therapy.