The current guidelines recommend prophylactic whole brain radiotherapy for small cell lung cancer patients, but the necessity of prophylactic whole brain radiotherapy should be judged in the light of the patient’s specific condition. Prophylactic whole brain radiotherapy, also known as prophylactic irradiation, refers to the implementation of brain radiotherapy before the emergence of imaging or clinical symptoms, and is currently mostly used for the prevention of brain metastasis of small-cell lung cancer, which is an undifferentiated cancer that progresses faster and is prone to brain metastasis, and the chemotherapeutic drugs can not pass the blood-brain barrier, so in view of such a situation, patients are often given prophylactic irradiation of the brain in the clinic. If there is no contraindication for patients, preventive brain radiotherapy is generally recommended, but the specific dose of radiotherapy should be considered in the light of patients’ conditions. It is recommended that patients actively cooperate with the treatment under the guidance of the doctor in order to prolong the survival period.