Inclusion Criteria:  Patients voluntarily participated in the clinical study, understood the study procedures and are able to sign the informed consent form. 18 to 75 years old, male or female. Histologically or cytologically confirmed extensive stage small cell lung cancer（ED-SCLC）. ECOG Performance Status of 0 or 1. Adequate hematological, hepatic and renal function. Female subjects of child-bearing potential must have a negative serum HCG test before treatment.  Exclusion Criteria:  Histologically or cytologically confirmed mixed SCLC and NSCLC. Untreated central nervous system metastases. Cancerous meningitis (meningeal metastasis). Uncontrolled pleural effusion, pericardial effusion or ascites. Tumor infiltration into the great vessels on imaging; Hemoptysis symptoms and maximum daily hemoptysis ≥ 2.5ml occurred within 1 month. Uncontrolled tumor-related pain. Malignancies other than SCLC within 5 years. Systemic antitumor therapy was received 4 weeks prior to trial treatment. History of autoimmune diseases. Significant cardiovascular disease. Inadequately controlled hypertension. Known history of testing positive test for HIV or known AIDS. Patients with active hepatitis B or hepatitis C Severe infections within 4 weeks prior to trial treatment. Active tuberculosis.