The glycoconjugate antigen CA19-9, a salivary acidified lactobiont valeric acid, is a component of mucin-like proteins and glycoproteins. In normal value testing, the reference value of CA19-9 is 0-37 U/mL. In clinical practice, CA19-9 can be significantly elevated in patients with pancreatic cancer, gallbladder cancer, and potbelly cancer, with some patients exceeding 10,000 or more. Especially in the advanced stage of pancreatic cancer, the value of CA19-9 can reach higher and the clinical positivity rate reaches more than 80%. However, the high value of CA19-9 cannot be used as the main basis for determining whether it is a tumor, because some inflammatory diseases, including acute pancreatitis, cholecystitis, cholestasis, and even cirrhosis of the liver, can cause an increase in CA19-9. Therefore, it is advocated to take the normal reference value of the two-fold test as the upper limit, and to conduct continuous dynamic observation for patients who exceed the index. If the laboratory index is persistently elevated, it suggests a potential risk of malignancy.