Radiotherapy for lung cancer is generally painless, and the main sites of radiotherapy are the lung mass and its metastatic lymph nodes, so the side effects are mainly skin reaction and radiation pneumonia. Therefore, the side effects are mainly skin reactions and radiation pneumonia. Among them, skin reactions are mostly repaired gradually after radiotherapy, while radiation pneumonia mostly occurs during radiotherapy and 1-2 months after radiotherapy, which can be manifested as cough and shortness of breath, and can be clearly diagnosed by chest X-ray or CT examination.