This study is a randomized, placebo-controlled, double-blind, multicenter phase III clinical study. Target population is patients with stage IV squamous non-small cell lung cancer who had not received systemic chemotherapy. Study objective is to compare the efficacy and safety of SHR-1210 + carboplatin + paclitaxel with placebo + carboplatin + paclitaxel in study population in China. SHR-1210 is a humanized anti-PD1 IgG4 monoclonal antibody.

In this study, eligible subject will be randomized into study arm or control arm to accept study treatment. Subjects who randomized into control will have the opportunity to receive cross over treatment of SHR-1210 monotherapy after confirmed disease progression. Treatment cycles of chemotherapy will be 4-6 which will be decided by investigators.

Inclusion Criteria:

1. Subjects with histopathological diagnosis of squamous non-small cell lung cancer (SqNSCLC) and clinical stage IV
2. has not received prior systemic treatment for metastatic NSCLC.
3. Has a performance status of 0 or 1 on the Eastern Cooperative Oncology Group (ECOG) Performance Status
4. Has archived Tumor tissue samples
5. Subject must have a measurable target lesion based on RECIST v1.1 .
6. Has adequate organ function.
7. Women of childbearing age must undergo a serological pregnancy test within 7 days before the first dose with negative results. Female subjects of reproductive age and male subjects whose spouse is a woman of reproductive age must agree to effective contraception within 180 days after the study period and the last dose of the study drug.
8. Subjects should be voluntarily participate in clinical studies and informed consent should be signed.

Exclusion Criteria:

1. active brain metastases and meningeal metastasis
2. uncontrollable tumor-related pain
3. massive pleural effusion, peritoneal effusion or pericardial effusion which cannot be controlled by repeated drainage;
4. radiotherapy to lung that is >30 Gy within 24 weeks before the first dose,
5. imaging (CT or MRI) showed that the tumor invading the large vessels
6. Known EGFR/ALK mutation.
7. subjects with any known or suspected autoimmune diseases
8. subjects with known or suspected interstitial pneumonia;
9. Subjects with severe cardiovascular and cerebrovascular diseases
10. arteriovenous thrombosis events, such as deep vein thrombosis and pulmonary embolism, occurred within 3 months;
11. female subjects who are pregnant or lactation or who plan to be pregnant during the study period;
12. positive HIV test;
13. active hepatitis B
14. evidence of active TB infection within 1 year before first dose;
15. severe infection occurred within 4 weeks before the first dose
16. patients with clinically significant bleeding symptoms or with obvious bleeding tendency in the first month
17. subjects who is on systemic immunogenic agents;
18. a history of severe allergic reactions to other monoclonal antibodies/fusion proteins;
19. History of severe allergic reactions to carboplatin or paclitaxel or their preventive drugs;