Gastric cancer is usually diagnosed clinically by the following methods: a. Gastroscopy, which can visually observe the specific situation inside the stomach of patients and is of great value for early gastric cancer diagnosis. Barium radiography can be combined with gastroscopy to observe the symptoms of filling defect and abnormal peristaltic movement of gastric mucosal folds in the stomach, which may be more likely to be gastric cancer. Laboratory tests, such as CEA, CA199, CA724, etc. are also important markers for gastric cancer diagnosis and postoperative treatment assessment.