Abstract: Peritoneal metastasis is one of the most frequent metastatic patterns of advanced gastric cancer, but the mechanism underlying remains unclear. The ‘seed and soil’ theory is now well recognized for peritoneal metastasis of gastric cancer at present. The combination of various cells, extracellular matrix, and ascites components within the abdominal cavity provide a suitable microenvironment for the plantation, infiltra-tion, growth and metastasis of gastric cancer cells. Fully under-standing of peritoneal microenvironment will help to diagnose the peritoneal metastasis of gastric cancer and tumor recurrence, and provide theoretical basis for the development of drugs targeting peritoneal microenvironment. The authors review the main cell formation, ascites and immune microenvironment involved in the formation of the peritoneal microenvironment based on relevant literatures at home and abroad, and investigate the relationship between peritoneal microenvironment and peritoneal metastasis of gastric cancer.