Stomach cancer has a certain genetic predisposition, but most patients with stomach cancer have little genetic relationship. In the current study, it is found that among some gastric cancer patients, the incidence of gastric cancer among their blood relatives is four times higher than that of their unrelated relatives, 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 certain role in gastric cancer. However, not all gastric cancers are hereditary, and the occurrence of gastric cancer is a multifactorial, multi-step and multi-stage development process. The exact cause of gastric cancer is still unclear, and many factors are related to the occurrence of gastric cancer. Stomach cancer in China is influenced by various factors such as poor dietary habits, chronic gastric disease and Helicobacter pylori infection, in addition to geography. Long-term consumption of smoked and pickled foods can easily lead to the occurrence of gastric cancer due to the presence of carcinogenic substances such as nitrosamines in food; H. pylori can lead to increased ammonia production in the digestive tract, which in turn causes inflammation and proliferation of gastric mucosa, causing DNA damage and can produce carcinogenic substances; some chronic diseases of the stomach such as chronic gastritis develop from gastritis to atypical hyperplasia to gastric cancer after about 10 years. In conclusion, the occurrence of gastric cancer has obvious geographical characteristics and is related to various factors such as poor dietary habits, H. pylori infection and chronic diseases of the stomach, etc. Only a small number of gastric cancer patients have genetic tendency, therefore, those who are found to have gastric cancer among their first-degree relatives need not be overly nervous and regular check-ups are sufficient.