The research level of gastric cancer screening is higher in Japan and the United States, and they have strong economic and technical strength to carry out large-scale screening, early diagnosis and early treatment in areas with high incidence of gastric cancer, and carry out endoscopic resection of the most early gastric cancer, or radical gastric cancer surgery, in order to achieve the goal of improving survival and reducing mortality. In Japan, physicians have been using X-ray double contrast imaging or/and gastroscopy techniques for screening for 30 years, screening about 4.5 million people at risk each year, with a sensitivity of 84% and specificity of 86.5%, and finding 40% to 50% of all gastric cancers in early stages. The 5-year survival rate after surgery for early gastric cancer is 80% and the 10-year survival rate is 78.5%. However, the cost of screening is very high, about $7,000 for each case of gastric cancer detected. To date, the World Health Organization and the International Union Against Cancer have not recommended this method to other countries. In the United States, serum pepsinogen I and II and their ratios are used as a screening method for gastric cancer, and large-scale screening has been implemented in Poland, and the results of the study have confirmed the effectiveness of screening for gastric cancer and precancerous diseases (atrophic gastritis). The Cancer Hospital of Chinese Academy of Medical Sciences started to screen for upper gastrointestinal tumors by occult blood test in 1984, and those with positive occult blood test were mobilized to undergo gastroscopy and biopsy when needed. By July 1993, a total of 242,296 people were screened with occult blood beads in 20 provinces and autonomous regions in China, and on average, 12.5% of the high-risk group were screened with occult blood beads, and 87.5% of them were negative with occult blood test. Among those with positive occult blood, 17,915 people underwent gastroscopy, and 638 people were pathologically diagnosed with cancer, of which early-stage cancer accounted for about 60%, and the average cancer detection rate under gastroscopy was 3.56%. Treatment was arranged for patients with gastric cancer. This has reduced the number of people undergoing gastroscopy, improved the efficiency and saved a lot of money. During the Seventh Five-Year Plan, Beijing Medical University and other universities implemented a probabilistic model of gastric cancer risk factors – ultra-micro gastric fluid series analysis and monoclonal antibodies as screening methods to screen 12,000 people in a sequential manner, with gastroscopy and pathological examination as the final diagnosis. The response rate was 90%, and the correct diagnosis rate of gastric cancer and precancerous lesions was 87% and 93%. The early cancer detection rate was 47%, and the five-year survival rate was 89%. In 1999, the Screening Program for Common Malignant Tumors in China recommended the following screening program for gastric cancer: (i) Selection of screening target: in the area with high incidence of gastric cancer, people aged 35-70 years are selected, accounting for about 1/3 of the total population, but about 96% of gastric cancer cases can be included. (ii) Screening methods: In addition to the methods described above, it is recommended to select from the following four methods or combinations: Ultramicrometric gastric fluid series screening method: Occult blood, pH, free acid, total acid, nitrite, pyloric snail secretory IgA antibody can be measured simultaneously in the target. Gastric fluid endogenous fluorescence spectroscopy screening method. Fresh gastric mucosal cell screening method. Anti-gastric cancer monoclonal antibody AH3 screening and immunohistochemical pathological diagnosis. (iii) Screening frequency: according to the screening study at the site of high prevalence of gastric cancer, thus it is considered that the screening interval should be once every 3 years for the general high prevalence population and once a year for patients with precancerous lesions. (iv) Detection of related diseases and treatment of precancerous lesions: Research on the so-called precancerous states and lesions related to the occurrence of gastric cancer provides the basis for improving the diagnosis rate of early gastric cancer. Regular follow-up of lesions closely related to the occurrence of gastric cancer may identify early gastric cancer or even micro gastric cancer. Lesions that belong to those requiring follow-up include chronic gastritis, intestinal epithelial hyperplasia of gastric mucosa, gastric polyps, remnant stomach, giant gastric crepitus sign, chronic gastric ulcer and heterogeneous hyperplasia of gastric epithelium. Patients mentioned above should be followed up regularly (0.5~2 years) in hospital, with endoscopy or X-ray double contrast imaging as the main follow-up examination method and mucosal biopsy examination when necessary, in order to detect early cancer.