Inclusion Criteria:  18 years old ≤ age ≤ 75 years old; The primary gastric lesion was diagnosed as gastric or esophagogastric junction adenocarcinoma (papillary adenocarcinoma, tubular adenocarcinoma, mucinous adenocarcinoma, signet ring cell carcinoma, and poorly differentiated adenocarcinoma. ) The tumor is located in the stomach or esophagogastric junction (Siewert type II/III) The preoperative clinical staging is cT4aNxM0, P0 or cTxNxM1*, P1 (*no other distant metastases except peritoneal metastasis) Good bone marrow reserve function: HB≥90g/L; ANC ≥1.5×10*9/L; PLT ≥80×10*9/L Good liver and kidney function reserve: BIL ≤ 1.5 times the upper limit of normal (ULN); ALT and AST ≤ 2.5×ULN; Crea≤1×ULN; Good coagulation function: International normalized ratio (INR) or prothrombin time (PT) ≤ 1.5 times ULN, activated partial thromboplastin time (APTT) ≤ 1.5 times ULN ECOG (Eastern Cooperative Oncology Group) physical status score 0-2; No prior treatment of chemotherapy, radiotherapy, targeted therapy, immunotherapy, etc; Written informed consent.  Exclusion Criteria:  There are distant metastases other than peritoneal metastases; Complications of gastric cancer require emergency treatment, such as bleeding, perforation, obstruction, etc.; Suffer from other malignant tumors within five years; Body temperature ≥38℃ or complicated with infectious diseases requiring systemic treatment; If there is a history of uncontrolled epilepsy, central nervous system disease, or mental disorder, the investigator will determine whether the clinical severity hinders the signing of informed consent or affects the patient's compliance with oral medications; Clinically serious (ie active) heart disease, such as symptomatic coronary heart disease, New York Heart Association (NYHA) grade II or more severe congestive heart failure, or severe arrhythmia requiring drug intervention, or recent history of myocardial infarction within 12 months; Severe respiratory diseases; Severe liver and kidney dysfunction; Upper gastrointestinal obstruction or abnormal physiological function or malabsorption syndrome, which may affect the absorption of oral drugs; Diseases such as severe diabetes, hyperthyroidism and hypothyroidism have not been clinically controlled. Those who continue to use glucocorticoid therapy within 1 month (except for local application) or who require immunosuppressive therapy for organ transplantation; Pregnant or lactating women; The patient has participated or is participating in other clinical studies (within 6 months);