• 1\. The subjects voluntarily joined this study, were able to complete the signing of the informed consent form, and had good compliance; 2. Age range from 18 to 75 years old (when signing the informed consent form), regardless of gender; 3. Gastric cancer or gastroesophageal junction adenocarcinoma confirmed by histology and/or cytology, diagnosed with local progression according to AJCC 8th edition standards, cT3-4N+M0 diagnosed with cTNM based on endoscopic ultrasound or enhanced CT/MRI scanning (combined with diagnostic laparoscopic exploration if necessary), and agreeing to undergo radical surgical treatment. The researcher evaluates the lesion as resectable; 4. Have not received systematic treatment for the current disease in the past, including anti-tumor radiotherapy, chemotherapy, immunotherapy, etc; 5. IHC results confirm HER2 expression (defined as IHC1+, 2+, 3+); 6. ECOG score 0-1 points; 7. Expected survival time ≥ 6 months; 8. The main organs are functioning well; 9. Fertility subjects must use appropriate methods of contraception during the study period and within 120 days after the end of the study. They must have a negative serum pregnancy test within 7 days before enrollment and must be non lactating subjects.