Inclusion Criteria:  Aged ≥ 18, regardless of gender . Histologically or cytologically confirmed small cell lung cancer . The time after the end of first-line treatment was less than 6 months . Subjects must have measurable diseases as defined in RECIST v1.1 . Eastern Cooperative Oncology Group (ECOG) performance status scores are 0-2 . Adequate hematologic and end organ function . Capable of understanding the trial nature and voluntarily signing the written informed consent form .  Exclusion Criteria:  Radiographic findings showed that the tumor involved large blood vessels or was poorly demarcated from them . Radiographic findings showed significant pulmonary cavitation or necrotizing tumor . Active brain metastasis or meningeal metastasis . With other malignant tumors in the past 5 years, except cancers that have been cured significantly or can be focally cured, e.g. basosquamous carcinoma of skin, or carcinoma cervix in situ . With Interstitial lung disease, including drug- induced Interstitial lung disease or radiation pneumonitis . With clinically significant cardiovascular disorder . Prior exposure to any immune checkpoint inhibitors, including but not limited to other anti-CTLA-4, anti-PD-1 or anti-PD-L1 antibodies . Prior exposure to anti-VEGFR therapy . Known hypersensitivity to study drug or any of its excipients . Treatment with any other investigational agent or participation in another clinical trial within 4 weeks prior to first administration . Other conditions that the investigator thinks unsuitable in this study .