Inclusion Criteria:  Signed written informed consent. Age strictly at least 70 years. Cytologically or histologically proven NSCLC(adenocarcinoma, epidermoid carcinoma, large-cell carcinoma) of locally advanced (stage IIIb/IIIc), metastatic, or relapsing (stage IV) according to the American Joint Committee on Cancer Staging Handbook. Presence of at least one measurable target lesion (RECIST rules) in a non irradiated region. No previous systemic chemotherapy for lung cancer. PD-L1≥50% in tissue samples detected by immunohistochemistry. PS 0 or 1. Life expectancy sup 12 weeks. Normal hematologic function.  Exclusion Criteria:  EGFR-sensitive mutations or ALK rearrangements Previous treatment with immune checkpoint inhibitors Presence of symptomatic brain metastases； Chinese patent medicine with anti-lung cancer indications or immunoregulatory drugs (including thymopeptide, interferon and interleukin, except for the local use of pleural effusion control) for systemic treatment； Another previous or concomitant cancer, except for basocellular cancer of the skin or treated cervical cancer in situ； Concurrent administration of one or several other antitumor therapies； Concurrent participation in another clinical trial； Active autoimmune disease requiring systemic treatment occurred within 2 years prior to initial； Systemic glucocorticoid therapy or any other form of immunosuppressive therapy within 7 days prior to initial administration； Contraindication to the study drugs； Has not fully recovered from toxicity and/or complications caused by any intervention prior to the commencement of treatment (i.e., grade 1 or baseline, excluding fatigue or hair loss); A history of human immunodeficiency virus (HIV) infection; Untreated active hepatitis B (defined as HBsAg positive and HBV-DNA copy number detected greater than the upper limit of normal value in the laboratory of the research center); Active HCV infected; Recent vaccination within 30 days before the first administration (cycle 1, day 1); Other severe concurrent disorders that occurred during the prior six months before enrollment (myocardial infection, severe or unstable angor, NYHA class 3 or 4 congestive heart failure, transient or constituted cerebral ischemic attack, psychiatric or neurological disorders preventing the patient from understanding the trial, uncontrolled infections).