Gastric cancer is one of the most common malignant tumors and is the second most common among digestive tract malignant tumors in China. Although most gastric cancers are epidemic in nature, some of them are obviously genetically related. The incidence rate of gastric cancer among blood relatives of gastric cancer patients is four times higher than that of the control group, and the proportion of their first-degree relatives suffering from gastric cancer is significantly higher than that of their second- and third-degree relatives, indicating that genetic factors play a role in the development of gastric cancer. About 5%-10% of gastric cancers have family aggregation tendency, and 3%-5% are associated with hereditary cancer syndrome. Hereditary diffuse gastric cancer is an autosomal dominant disease caused by mutations in the oncogene epithelial-calcineurin (CDH1), which is mainly characterized by the occurrence of gastric cancer at a young age, with an average age of 37 years, and mostly diffuse gastric cancer. The prevalence of gastric cancer at age 80 is 67% in men and 83% in women. Genetic alterations in other hereditary cancer syndromes are also associated with gastric carcinogenesis, such as epithelial cell adhesion molecule (EPCAM) genes associated with Lynch syndrome and APC genes associated with familial adenomatous polyposis. Therefore, patients with these hereditary cancer syndromes need to be closely followed up with gastroscopy for timely detection of gastric cancer. Recent molecular biology studies have shown that gastric mucosal carcinogenesis is a multifactorial, multistep and multistage developmental process involving multiple oncogenes, oncogenes apoptosis-related genes and metastasis-related genes.