Purpose: To evaluate the effect of radiotherapy and to detect the prognostic factors for residual and recurrent foci after surgery of thyroid gland cancers. Materials and Methods: 109 patients with residual or recurrent foci of thyroid cancers after surgery were treated with radiotherapy. Results:The overall 5-,10-, 15-, 20- and 25- year survival rates were 93.6%, 91.7% , 88.7%, 87.6% and 87.6% and the 5-, 10-, 15-, 20- and 25- year survival rates with no evidence of disease were 90.8%, 89.8% ,85.6%, 84.1% and 84.1%, respectively. The clinical stage was the main factor and patient's age at diagnosis, patient's sex, histopathological types and radiation dose were also the prognostic factors. Conclusion:Radiotherapy is beneficial to residual and recurrent foci after surgery of thyroid cancer. The optimum radiation dose is 45～65 Gy.