The most accurate diagnosis of gastric cancer is gastroscopy and pathological biopsy. Besides, X-ray barium meal, CT, laboratory examination and other auxiliary diagnosis can also be performed. Gastroscopy is the most accurate method to diagnose gastric cancer, which can directly observe the position and scope of gastric mucosal lesions through mirror, as well as take biopsy for pathological examination, and ultrasonic gastroscopy can clarify the invasion depth of gastric cancer. Among them, pathological diagnosis is the gold standard. X-ray barium meal is also a common method to diagnose gastric cancer, and gas-barium double contrast can observe the filling of mucosa to diagnose. CT examination can clearly determine whether there is metastasis of gastric cancer, and can also see whether gastric cancer involves gastric wall and grows inside and outside the cavity and its range. Laboratory tests include stool routine, fecal occult blood test, blood routine, etc. There are also tumor markers, such as carcinoembryonic antigen CA724, cancer antigen CA19-9, CA125, etc. These values are helpful to diagnose gastric cancer.