Precancerous state of gastric cancer refers to pre-cancerous gastric diseases, such as chronic atrophic gastritis, gastric ulcer, gastric polyp, residual gastritis and hypertrophic gastritis, etc. These benign gastric diseases may occur as gastric cancer. Among them, chronic atrophic gastritis is the most common pre-cancerous state of the stomach. Scholars at home and abroad have followed up chronic atrophic gastritis and found that up to 10% of chronic atrophic gastritis is carcinogenic. The main pathological features of chronic atrophic gastritis are chronic inflammation of mucosa and glandular atrophy, accompanied by intestinal hyperplasia and atypical hyperplasia of gastric mucosa. The timely detection of precancerous state of gastric cancer, strengthening regular review and taking preventive measures can prevent or detect gastric cancer at an early stage.