This study is a single center, phase II study, to evaluate the effectiveness and safety of PD-1 Antibody(SHR-1210) Plus apatinib Combined With POF(paclitaxel plus oxaliplatin plus 5-fluorouracil plus leucovorin) , in the first-line treatment for patients with advanced/metastatic gastric cancer.

This is a exploratory, single-arm, open-label trial. The investigator's primary purpose is to compare that ORR of patients with camrelizumab plus apatinib and POF for advanced/metastatic gastric cancer.

In treatment period, patients will be administrated camrelizumab plus apatinib and POF, every 28 days for 1 cycle, until disease progression, toxicity intolerance, withdrawal of informed consent, patients judged must be terminated study termination.

The imaging evaluation was performed according to the RECIST 1.1 criteria every 8 weeks.

Inclusion Criteria:

1. Patients with advanced unresectable, histologically confirmed adenocarcinoma of the gastric or gastroesophageal junction.
2. No previous treatment with chemotherapy or radiation therapy.
3. Ability to take medications orally.
4. With measurable lesions,according to Response Evaluation Criteria In Solid Tumors Version 1.1.
5. Patients must have a performance status of 0-1 on the Eastern Cooperative Oncology Group (ECOG) scale.
6. Without serious system dysfunction and could tolerate chemotherapy. With normal marrow, liver and renal function: a hemoglobin (HGB) of ≥100g/L (without blood transfusion during 14 days); a leucopenia count of ≥4.0×109/L; a platelet count of ≥100×109/L; a total bilirubin (TBil) of ≤1.5 upper normal limitation (UNL); a creatinine (Cr) of ≤ 1.5 UNL; a creatinine clearance rate ≥ 50ml/min (Cockcroft-Gault); a alanine aminotransferase (ALAT) and aspartate aminotransferase (ASAT) of ≤2.5 UNL or ≤5 UNL in case of liver metastasis.
7. Life expectancy ≥3 months.
8. Female subjects of child-bearing potential must agree to use contraceptive measures starting 1 week before the administration of the first dose of apatinib until 8 weeks after discontinuing study drug. Male subjects must agree to use contraceptive measures during the study and 8 weeks after last dose of study drug With written informed consent signed voluntarily by patients themselves or their supervisors witted by doctors.
9. With good compliance and agree to accept follow-up of disease progression and adverse events.

Exclusion Criteria:

1. Patients with a history of another neoplastic disease within the past three years, excluding basal cell carcinoma of the skin, cervical carcinoma in situ, or nonmetastatic prostate cancer.
2. With any acitve autoimmune disease or history of autoimmune disease, including but not limited to the following: hepatititis, pneumonitis, uveitis, colitis (inflammatory bowel disease), hypophysitis, vasculitis, nephritis, hyperthyroidism, and hypothyroidism, except for subjects with vitiligo or resolved childhood asthma/atopy. Asthma that requires intermittent use of bronchodilators or other medical intervention should also be excluded.
3. Hypertension and unable to be controlled within normal level following treatment of anti-hypertension agents: systolic blood pressure > 140 mmHg, diastolic blood pressure > 90 mmHg.
4. Clinically significant cardiovascular and cerebrovascular diseases, including but not limited to severe acute myocardial infarction within 6 months before enrollment, unstable or severe angina, Congestive heart failure (New York heart association (NYHA) class > 2), orventricular arrhythmia which need medical intervention.
5. Known history of hypersensitivity to any components of the SHR-1210 formulation, or other antibody formulation.
6. Prior systemic chemotherapy, radiotherapy, immunotherapy, hormone therapy, surgery or target therapy within 4 weeks.
7. Coagulation abnormalities (PT>16s、APTT>43s、TT>21s、Fbg<2g/L), with bleeding tendency or are receiving thrombolytic or anticoagulant therapy.
8. Has known active central nervous system metastatases.
9. Pregnant (positive pregnancy test) or breast feeding.
10. History of a stroke or CVA within 6 months. Clinically significant peripheral vascular disease.
11. Inability to comply with study and/or follow-up procedures. Patients with any other medical condition or reason, in that investigator's opinion, makes the patient unstable to participate in a clinical trial.