The serum fucosidase (AFU) value in normal adults was 27.15±128 U/L by the rate method, and 6.9±3.4 U/L in healthy adults by the endpoint method.Fucosidase is a tumor marker, and its elevation is of great value in the determination of hepatocellular carcinoma. Fucoidan is essentially a glycoprotein, lysosomal acid hydrolase. It is widely distributed in human cells and body fluids, and is involved in the decomposition of various glycolipids, glycoproteins and other macromolecules. The results are different when measured in different ways. Using the rate method, the normal adult serum fucosidase (AFU) value is 27.15±128 U/L. Using the endpoint method, the AFU value is 6.9±3.4 U/L. Fucoidan is a tumor marker for primary hepatocellular carcinoma, which is also elevated to varying degrees in other liver diseases such as metastatic hepatocellular carcinoma, cholangiocarcinoma, and mesenchymal mesothelioma. Elevated fucoidan alone cannot confirm the diagnosis of a certain disease, and relevant examinations should be completed and standardized treatment should be prescribed by the doctor.