Abstract: Thyroid carcinoma is the most common malignant tumor of the endocrine system， which can be divided into four kinds according to the pathological type： papillary thyroid carcinoma， follicular thyroid carcinoma， medullary thyroid carcinoma and undifferentiated thyroid cancer. The first two are known together as differentiated thyroid cancer due to the high level of differentiation. The initial management of differentiated thyroid cancer is surgery， followed by radioactive iodine for gross residual or unresectable disease. For both differentiated thyroid cancer and medullary thyroid cancer， the role of external beam radiotherapy after resection of gross disease when there is a high risk of local regional failure is reviewed. Accurate radiotherapy can reduce the risk of the local recurrence and the radiation injury to normal tissue. In anaplastic thyroid cancer， although most patients present with unresectable disease and radiotherapy is the mainstay of treatment， the benefits of the addition of chemotherapy to radiation therapy will be discussed. External beam radiotherapy not only plays a role as a part of combined treatment of preoperative and postoperative， but also can be used separately to alleviate symptoms， control the growth of the lesion and prolong the overall survival to serve the purpose of palliative treatment.