Inclusion Criteria:

1. Patients must provide written informed consent.
2. age 18 to 75;Confirmed as a primary gastric adenocarcinoma patient by imaging and histology or cytology;
3. Patients with advanced gastrointestinal cancer who have received no prior chemotherapy or radiotherapy for malignant tumors;
4. Patients with Eastern Cooperative Oncology Group Performance Status of 0 or 1.
5. Patients with a life expectancy of at least three months.;
6. Organ function and hematopoietic function must meet the following requirements: hemoglobin (HGB) ≥ 90g / L; white blood cell count (WBC) ≥ 3 × 10 ^ 9 / L; absolute neutrophil count (ANC) ≥ 1.5 × 10 ^ 9 / L Platelet count (PLT) ≥ 100 × 10 ^ 9 / L; total bilirubin (TBIL) ≤ 1.5 × upper limit of normal (ULN); aspartate aminotransferase (AST) and alanine aminotransferase ( ALT)≤2.5×ULN; if abnormal liver function is due to tumor liver metastasis, AST or ALT≤5×ULN; serum creatinine (Cr)≤1.5×ULN; international normalized ratio (INR) or plasma prothrombin time ( PT) ≤ 1.5 × ULN.
7. Systolic blood pressure 90-140mmHg, diastolic blood pressure 60-90mmHg, heart rate 60-100bpm.
8. No previous cardiovascular and cerebrovascular diseases, and exclusion of atrioventricular block by 24-hour ambulatory electrocardiography;
9. subjects must agree to take effective contraceptive measures between the subject and the partner after signing the informed consent, during the study period and within 5 months after the last dose.

Exclusion Criteria:

1. There are clinical symptoms or diseases of the heart that are not well controlled, such as uncontrolled high blood pressure, unstable angina, or myocardial infarction within 6 months prior to enrollment, or poorly controlled arrhythmias (including QTc ( men ≥ 450ms , female ≥ 470ms, QTc interval calculated by Fridericia formula), cardiogenic shock, heart block (II-III degree atrioventricular block), severe or acute heart failure, sinus bradycardia, need continuous oxygen Treated severe respiratory diseases;
2. Subjects with symptomatic autoimmune diseases [such as, but not limited to, interstitial pneumonia, uveitis, enteritis, hepatitis, pituitary inflammation, vasculitis, nephritis, hyperthyroidism, decreased thyroid function; The tester has vitiligo or has completely relieved asthma in childhood, and can be included without any intervention after adulthood; asthma that requires bronchodilators for medical intervention cannot be included]
3. Patients with other malignant tumors within 5 years prior to enrollment, in addition to appropriate treatment of cervical carcinoma in situ, cured skin basal cell carcinoma;
4. Immunodeficiency, such as a patient with HIV infection or other acquired, congenital immunodeficiency disease, or a history of organ transplantation
5. Patients with active tuberculosis infection by medical history or CT examination, or a history of active tuberculosis infection within 1 year prior to enrollment, or patients with a history of active tuberculosis infection more than 1 year without formal treatment;
6. Patients with tumor brain metastasis and bone marrow metastasis
7. Patients who participated in other drug clinical studies within 4 weeks;
8. Patients with history of hypersensitivity to any drugs in this study;
9. Identified as neurological or psychiatric disorders, such as epilepsy, dementia, poor compliance;
10. Alcohol abuse, drug abuse in the past year;
11. Hepatitis B surface antigen (HBsAg) positive and hepatitis B virus DNA (HBV DNA) > 10 ^ 3 copies / mL, or hepatitis C virus antibody positive; syphilis positive;
12. Subjects had active infection or unexplained fever >38.5 degrees during Screening period before the first dose (according to the researcher, the subject can be enrolled due to fever generated by the tumor.);
13. Clinical symptoms of ascites or pleural effusion, requiring therapeutic puncture or drainage;
14. Female patients who are pregnant or lactating, or planning to become pregnant or lactating;
15. Other patients who are considered to be unsuitable for this study by the investigator.