1.Dietary factors: Diet is closely related to the development of gastric cancer, and the incidence of gastric cancer in developed countries in Europe and America has been decreasing in recent years, which is mainly related to dietary factors. This is mainly related to dietary factors, which are characterized by the following: in the past, food was preserved by smoking (smoked fish, smoked meat) and salt curing methods, which contain quite high carcinogens, such as benzo(a)pyrene and nitrosamines, while high concentration of salt is considered as carcinogenic substances. Food fried in high-temperature oil also contains a certain amount of polycyclic aromatic hydrocarbons carcinogens. Talcum powder is commonly used to treat rice in Japan, and talc contains carcinogenic asbestos fibers. High-salt foods such as cured meat, cured fish, cured poultry, pickled vegetables, bacon and salami are also noted because high-salt foods can damage the gastric mucosa and make carcinogens easily absorbed by the body. A survey in China’s Henan Province showed that salt consumption was significantly and positively correlated with gastric cancer mortality. The lack of protein, fat, certain vitamins and minerals in the diet of certain people makes the host nutrition unbalanced, thus reducing the body’s resistance, which directly or indirectly facilitates the occurrence of gastric cancer. 2. Nitrosamines and other chemical substances: Currently, it is found through experiments that a variety of nitrosamines with different structures can cause gastric cancer in animals. Investigation on the high incidence of gastric cancer found that the content of nitrate and nitrite in drinking water and food is significantly higher than that in the low incidence area. Under the suitable PH value or the action of bacteria, nitrate and nitrite can synthesize carcinogenic nitrosamines in the human stomach. Small amounts of carcinogenic nitrosamines are also found in some cured meat, fish, poultry, vegetable foods, and foods treated with nitrite such as sausage, ham, luncheon meat and cured meat products. In addition, it has been reported that nitrosamines can be detected in cheese, milk, flour, beer and other liquors in some domestic and foreign countries. Nitroso compounds are used in industry as solvents, lubricants, rust inhibitors, etc., and in agriculture as pesticides, herbicides, etc., and can have occupational exposure. 3.Mycotoxin: Through epidemiological survey, it is found that the mold contamination of food and food in the high incidence area of gastric cancer in China is quite serious. The detection rate of mycobacteria and their toxins in fasting gastric juice of patients with chronic gastric disease in high incidence areas is significantly higher than that in low incidence areas of gastric cancer. Gastric fluid detected Aspergillus, Aspergillus flavus, Aspergillus oryzae and other molds, produced by the Aspergillus oryzae toxins can induce gastric cancer in rats. 4.Smoking and drinking: the incidence of gastric cancer increases significantly among long-term smokers. The longer the age of smoking, the more the incidence of gastric cancer. Smoking has carcinogenic and pro-carcinogenic effects on the stomach. Long-term alcohol consumption and other factors leading to stomach cancer have synergistic and pro-cancer effects. 5.H. pylori (HP) infection: H. pylori infection in the stomach is one of the important factors in the occurrence of gastric cancer, and the World Health Organization has designated H. pylori as a primary carcinogen for the occurrence of human gastric cancer. In 1994, Forman (UK) concluded that 35% of gastric cancer cases in developed countries and 85% in developing countries were associated with HP infection. Some scholars believe that HP infection may be a synergistic carcinogenic factor of gastric cancer. Genetic factors: Most of the retrospective survey materials believe that the role of genetic factors in the etiology of gastric cancer is relatively certain, and there is an obvious tendency of family gathering. It is generally believed that the incidence rate of gastric cancer among relatives of gastric cancer patients is 4 times higher than that of the control group. 7. Chronic gastritis: There is a close relationship between gastric cancer and chronic gastritis, especially atrophic gastritis. The incidence of this type of gastric cancer is related to the severity of atrophic gastritis and the length of medical history. Due to atrophic gastritis, the mucosal function and structure are abnormal, the free acid of gastric juice is reduced and the bacteria in gastric juice is increased, which increases the synthesis of nitroso compounds, which have been proven to cause gastric cancer. 8.Other: such as gastric mucosa intestinal epithelial metaplasia, gastric ulcer, gastric polyp patients are also high-risk groups of gastric cancer.