Radiotherapy for small cell lung cancer is to make cancer cells undergo necrosis and disintegration through radiation, so as to make cancer foci shrink or disappear, and achieve the therapeutic effect of controlling the progression of small cell lung cancer, so that patients can obtain clinical cure or symptomatic relief. Small cell lung cancer is highly sensitive to radiotherapy, so radiotherapy is one of the important treatment modalities for patients. According to the different purposes of radiotherapy, it is generally divided into two kinds: radical radiotherapy and palliative radiotherapy, in which radical radiotherapy is mainly used for patients with limited-stage small cell lung cancer, which is synchronized with chemotherapy, and may lead to clinical cure for small cell lung cancer patients. Palliative radiotherapy is mainly used for patients with extensive stage small cell lung cancer, which is mainly used in conjunction with systemic chemotherapy to control the development of small cell lung cancer, and it can mainly alleviate the clinical symptoms of the patients, such as chest pain, cough, hemoptysis and so on.