Perioperative drug treatment has gradually become the standard regimen for locally advanced gastric cancer, whereas only a subset of patients could benefit from it. Therefore, one major challenge for perioperative drug treatment is to construct promising biomarkers and to screen out potential beneficial patients. Recent evidence has revealed that tumor microenvironment (TME) is highly associated with the prognosis of gastric cancer. Meanwhile, tumor microenvironment score (TMEscore) established with transcriptomic data is a robust biomarker for predicting prognosis and guiding individualized immunotherapy strategies. However, its predictive value for perioperative drug treatment outcomes warrants further exploration and validation. The study is a multi-center, observational study to evaluate the relationship between the efficacy of perioperative treatment and tumor microenvironment in patients with locally advanced resectable gastric and gastro-oesophageal junction adenocarcinoma, aiming at further determining the predictive value of TMEscore and establishing a comprehensive treatment-efficacy evaluation system for gastric cancer.