Lung cancer is one of the most common malignancies and is currently the number one killer of cancer. Non-small cell accounts for 80% of all lung cancer cases, but only 20-30% of all lung cancer cases are operated, and distant metastases have been found in 30-40% of patients at the time of diagnosis. Radiotherapy is one of the most important treatment tools, which can be used not only for the treatment of local lesions (early stage and late stage), but also for advanced patients, a reasonable choice of radiotherapy will achieve satisfactory palliative treatment effect. Mechanism of radiotherapy? Radiotherapy is to treat tumors by using the difference in repairing ability and proliferating ability between tumors and normal tissues by rays or particles. Normal tissue cells will proliferate and repair after irradiation to compensate for the normal cells killed by radiation, while tumors will also proliferate, but because of their insufficient vascular supply, their proliferative ability is defective compared with normal cells, and their repair ability is poor after irradiation. About 45% of tumor patients can survive for more than 5 years after reasonable comprehensive treatment, of which the contribution rate of surgery is 22%, radiotherapy is 18% and chemotherapy is 5%. Indications of radiotherapy for lung cancer 1.Stage I (T1~N0M0): For those who are contraindicated to surgery or refuse surgery for medical reasons, radical radiotherapy with or without chemotherapy should be given. 2.Stage II that cannot be surgically resected for medical reasons: The preferred treatment modality for stage IIIa and IIIb NSCLC is combination therapy with radiation plus or without chemotherapy. 3.Stage IV feasible palliative radiotherapy. 4.Pre-operative radiotherapy: patients with critical possibility of surgical resection, apical lung cancer. 5.Postoperative radiation therapy indications (1) residual granuloma in surgery; (2) positive tumor in pathological examination of surgical specimen cut edge; (3) no mediastinal lymph node dissection in surgery. Postoperative radiation therapy can be considered in the following cases: (1) Patients with pathological examination of the surgical specimen showing hilar lymph node metastasis N1 and/or mediastinal lymph node metastasis N2, especially if the tumor has penetrated the lymph node envelope into the surrounding tissues; (2) Patients at high risk of lymphatic and hematologic metastasis as indicated by pathological and laboratory findings. Contraindications of radiotherapy for lung cancer 1.Patients with large amount of uncontrolled pleural effusion. 2.Patients with cachexia.