The purpose of this study is to investigate the efficacy and safety of intraperitoneal and intravenous nab-paclitaxel plus Camrelizumab and S-1 conversion therapy for gastric cancer with positive exfoliative cancer cells.

Inclusion Criteria:

1. None previous chemotherapy, radiotherapy and other antitumor therapy;

2. Age:18 to 70 years old;

3. Man or female (except pregnant and lactating women);

4. Confirmed to gastric adenocarcinoma and HER2-negative;

5. Proven gastric cancer of T stage was T3 and T4, and no distant metastasis was observed. The exfoliative cancer cells detection in peritoneal washes was positive;

6. Blood cell count has to meet the following certeria:

   WBC≥3.5×109/L; ANC≥1.5×109/L; PLT≥100×109/L; HB≥90g/L;

7. Liver/kidney function has to meet the following certeria:

   ALT and AST≤2.5×ULN TBIL<1.5×ULN； Serum creatinine ≤1.5×ULN;

8. Left ventricular ejection fraction (LVEF) ≥50%;

9. Eastern Cooperative Oncology Group (ECOG) performance status of 0-1;

10. Participants were willing to join in this study, good adherence and written informed consent.

Exclusion Criteria:

1. Subjects with immunosuppressive medications within 14 days of first administration of study treatment, excluding nasal spray and inhaled corticosteroids or physiological doses of systemic steroid hormones (no more than 10 mg / day of prednisolone or other corticosteroids of equivalent pharmaceutical physiological dose);
2. The patient has any active autoimmune disease or a history of autoimmune disease (such as the following, but not limited to: autoimmune hepatitis, interstitial pneumonia, uveitis, enteritis, hepatitis, pituitary inflammation, vasculitis, nephritis, hyperthyroidism, hypothyroidism; patients with vitiligo; Asthma has been completely relieved in childhood, and patients who do not need any intervention after adulthood can be included; asthma patients who require bronchodilators for medical intervention cannot be included);
3. Patients with other malignant tumors within 5 years;
4. Human immunodeficiency virus (HIV) infection or acquired immunodeficiency syndrome (AIDS), active hepatitis B (HBV-DNA ≥1000 IU/ml) or hepatitis C (positive hepatitis C antibody, and HCV-RNA is higher than the lower limit of detection of the analytical method) or co-infection with hepatitis B and C, requiring antiviral treatment during the study;
5. Distant metastasis;
6. It has serious or uncontrolled medical diseases and infections (Including atrial fibrillation, angina pectoris, cardiac insufficiency, ejection fraction less than 50%, poor-controlled hypertension and so on);
7. History of psychiatric drugs abuse and can't quit or patients with mental disorders;
8. Patients with severe or uncontrollable mental illness;
9. It have serious harm to the patient's safety or affect the patients who have completed the research.
10. The researchers think inappropriate.