The course of immunotherapy for small cell lung cancer cannot be completely determined, patients with effective treatment usually need to continue to use the drug for two years, and generally need to do immunotherapy for about 12 courses a year. Clinically, immunotherapy is mainly used for the treatment of extensive stage small cell lung cancer. At present, the immunotherapy drugs approved for clinical use include atilizumab, divalizumab and other immunotherapy drugs, which are mostly used in combination with systemic chemotherapy, and can improve the remission rate of the disease as well as prolong the survival of the patients if the treatment is effective. The combination of immune drugs and chemotherapeutic drugs is used for the first-line treatment of extensive-stage small-cell lung cancer, and patients who are effectively treated with six cycles of the combination regimen can continue to use immune drugs to maintain the treatment for two years.