Thymoma is aggressive and persistent, but does not belong to malignant tumors. In treatments, their optimal treatment protocols still need to be studied and how about the role and the place of use of postoperative radiotherapy is not clear. Some retrospective studies indicate a direction: for the first stage of thymoma, it is adequately treated with complete resection alone. For the second stage of the thymoma, postoperative radiotherapy needs further indications. For the third and fourth stages of thymoma, postoperative radiotherapy plays an important role. A research shows that the radiation dose at 50 Gy is suitable for microscopic tumors, and higher dose of radiation is suitable for macroscopic tumors. With the development of radiotherapy technology, its application scope becomes larger and larger. What kind of the role and the place for radiotherapy in the treatment of thymoma and what is the optimal management of thymoma need to be treated prudently.