Radiotherapy is one of the most important means of lung cancer treatment. Among the various types of lung cancer, small cell lung cancer is the most sensitive to radiotherapy, followed by squamous lung cancer and then adenocarcinoma. Therefore, radiotherapy may cause certain damage to different types of lung cancer patients, which may result in the following four major side effects: First, radiation pneumonia. This is an inflammatory reaction caused by radiation damage to normal lung tissues, which is mostly asymptomatic in mild cases, but may lead to cough, chest pain, shortness of breath, fever or even respiratory failure in severe cases. The main symptoms are shortness of breath, dry cough, and possibly fever and yellow sputum. It usually appears within a few months after adequate radiotherapy for lung cancer. The third is hair loss. When brain metastasis occurs in lung cancer, radiotherapy may be given to the head, which usually causes hair loss in different degrees. Fourth is radiation brain reaction. After brain metastasis occurs in lung cancer patients, it may cause cerebral edema and intracranial hypertension after whole brain or local brain radiation irradiation, which mainly manifests as headache and vomiting. In the course of clinical treatment, we also encountered some patients or family members who are very worried about these side effects. In fact, radiotherapy is a local treatment, and if the radiotherapist is experienced and accurate, he can protect the normal tissues as much as possible. Serious side effects are generally less likely to occur and are stage-specific. For example, if the tumor grows around the esophagus, radiotherapy will inevitably irradiate the esophagus, and some patients may develop radiation esophagitis at this stage, but it will gradually decrease or disappear after a period of time as the treatment progresses. In addition, radiotherapy needs to penetrate the skin and normal tissues to reach the tumor tissue, so it is inevitable that normal tissues will be irradiated. This is a complicated process, and doctors need to understand the location and size of the tumor, as well as the stage, stage and pathological type of the disease before they can give a clear treatment plan to the patient. For example, which areas are within the irradiation, which areas need to be identified for protection, the total dose of the treatment plan, the dose of each time, etc., all have to be determined according to the patient’s specific situation. Although radiation therapy for lung cancer may bring certain side effects to patients, until better treatment options are available, radiation therapy is still the best choice for some patients. Patients need to strengthen their exercise and physical fitness appropriately to ensure that the treatment can be carried out smoothly.