Children are less likely to develop stomach cancer, and the causes of stomach cancer include geographic environment, diet, and lifestyle, as well as factors such as Helicobacter pylori infection, chronic diseases, heredity, and genetics. If a child suffers from stomach cancer, the most likely cause is diet as well as genetic factors. The incidence of stomach cancer is higher in people who have been consuming smoked and salted foods for a long time, which is related to the content of carcinogens such as nitrites, fungal toxins, and polycyclic aromatic hydrocarbon compounds in the food. High-salt diet will destroy the protective layer of gastric mucosa, so that carcinogens will come into direct contact with the mucosa, and the lack of fresh vegetables and fruits in food is also a factor of incidence. The incidence rate of relatives of gastric cancer patients is four times higher than that of normal people, and the rate of first-degree relatives suffering from gastric cancer is higher than that of second- and third-degree relatives. Uncontrollable factors such as heredity and genes cannot be changed, but dietary factors can be prevented.