Stomach cancer is one of the most common malignant tumors in China, and we are not surprised to see it. But unfortunately, the diagnosis rate of early gastric cancer in China, a country with a high incidence of gastric cancer, is not high, only less than 20%. In Japan, on the contrary, early-stage gastric cancer accounts for the majority of diagnosed gastric cancer patients. Although the country as well as our medical personnel are constantly making efforts to diagnose and treat stomach cancer at an early stage, it is obvious that it is also very important to raise awareness of self-protection as an ordinary person. Patients with gastric cancer who obtain early diagnosis are able to achieve a 5-year survival rate of 95%, which means clinical cure, while modern gastroscopy technology and capability have been able to detect precancerous lesions and turn gastric cancer before it becomes invisible. However, the outcome of advanced gastric cancer is not optimistic. In fact, the diagnosis of early gastric cancer and precancerous lesions is not without traces, but people need to raise awareness of prevention. Gastroscopy is the most important tool to diagnose early gastric cancer and precancerous lesions.1. Age is obviously an important factor, and people over 40 years old need to be more alert (especially men). If upper abdominal symptoms, including upper abdominal pain, occur in the near future, or if the degree, nature and regularity of the original upper abdominal symptoms change, it is also important to see a doctor and undergo gastroscopy.2. If a close relative has gastric cancer, it is more important to see a doctor promptly if there is upper abdominal discomfort.3. Patients with previous atrophic gastritis Patients with previous chronic atrophic gastritis should undergo regular gastroscopy, especially for severe atrophic gastritis. Patients with chronic atrophic gastritis should undergo regular gastroscopy, especially those with severe atrophy and severe intestinal metaplasia. In general, patients with mild atrophic gastritis should have their gastroscopy reviewed once every five years. In moderate atrophic gastritis, gastroscopy is repeated every three years; in moderate atrophic gastritis, gastroscopy is repeated every one year. If heterogeneous hyperplasia is found on top of atrophic gastritis, gastroscopy should be repeated more frequently. Mild heterogeneous hyperplasia needs to be reviewed for the first time within 1 year. Those who have bad habits should pay more attention to gastroscopy, such as those who smoke, drink alcohol and eat inappropriately. 5. People who live in areas with high incidence of gastric cancer should pay more attention to gastroscopy because environmental and dietary factors may affect the occurrence of gastric cancer. People living in high incidence areas should pay attention to the screening of gastric cancer by gastroscopy. In recent years, with the advancement of endoscopic technology, lesions with moderate or severe heterogeneous hyperplasia or even early cancerous lesions can be removed by gastroscopy with full clarification of the scope and depth of the lesion, which can determine the presence of cancer on the one hand and remove the lesion on the other. The treatment of heterogeneous hyperplasia greatly reduces the chance of gastric cancer. People with early gastric cancer do not need further surgical procedures if they meet the criteria of safety after postoperative evaluation of the resected specimen. Long-term quality of life can be ensured. As for the early detection of gastric cancer and precancerous lesions and the determination of the diagnosis and treatment plan, it is wise to leave it to a professional and experienced endoscopist. Defy strategically, value tactically; do not ignore, do not fear. Lethargy, weakness, anemia, black stool, vomiting blood, and masses found in the upper abdomen are alarming signs to which doctors attach great importance and should consult a gastroenterologist for gastroscopy after the appearance of these phenomena. Of course, these symptoms are already relatively obvious and can hardly be called early diagnosis.