CA199 is not high in gastric cancer and can be normal, unless advanced gastric cancer involving the biliary tract and pancreas may be mildly elevated. The main tumor markers of the digestive system are carcinoembryonic antigen CEA, alpha-fetoprotein AFP, glycoantigen CA199 and glycoantigen 72-4. Gastrointestinal cancer is mainly elevated CEA and CA72-4; pancreatic or biliary malignant disease is mainly elevated CA199; liver malignancy is mainly elevated AFP. However, the specificity and sensitivity are not particularly high. Some patients can have normal tumor markers, and benign diseases of related organs can also be elevated. In clinical practice, multiple tumor markers are often combined to improve the positive rate, but the diagnosis can only be confirmed by the patient’s clinical symptoms and gastroscopic examination.