In recent years, as the incidence of lung cancer increases, lung cancer patients are more common in clinical practice. In the treatment of lung cancer, radiotherapy is one of the main methods of lung cancer treatment, which has been tested by clinicians for many years, but radiotherapy has some side effects while killing cancer cells. 1. Brain metastasis often occurs in alopecia areata lung cancer, and radiotherapy should take into account the metastases in the brain. Therefore, radiotherapy to the head is required, and radiotherapy to the head will generally cause hair loss to varying degrees. 2.Radiation brain reaction After brain metastasis occurs in lung cancer patients, whole brain or local brain radiation is often performed to control brain metastasis. However, after whole brain or local brain radiation irradiation, it may cause cerebral edema and intracranial hypertension, mainly manifested as headache, bad gas and vomiting, etc. 3.Radioactive pulmonary fibrosisThe main symptoms of radioactive pulmonary fibrosis include shortness of breath, dry cough, etc. If there is secondary infection, there may also be fever, yellow sputum and other symptoms. In addition, radioactive pulmonary fibrosis often appears within a few months after adequate radiotherapy for lung cancer. 4. Acute radiation pneumonia mostly occurs at doses above 40Gy, which is an inflammatory reaction caused by damage to normal lung tissues in the radiation field. The effect of radiotherapy on hematopoiesis of lung cancer is not as great as chemotherapy, but synchronous radiotherapy and chemotherapy will aggravate bone marrow suppression, in the process of tumor treatment, no treatment method is perfect, whether it is radiotherapy, chemotherapy or surgery, the treatment process will cause certain harm to patients, but it is easier to accept compared with tumor, so if some patients really need radiotherapy, they should still insist on it. Therefore, if some patients really need radiotherapy, they should still insist on it and should not choke on it. It is only to pay attention to the patient’s physical condition during radiotherapy and try to do some protective measures to reduce the patient’s pain. It is recommended to take more protein selenium, which can effectively prevent the decline of white blood cells and red blood cells, enhance appetite, prevent vomiting, diarrhea and swelling, improve sleep, reduce hair loss and reduce the pain of radiotherapy.