Abstract： Objective　To determine the changes of serum glycosylphosphatidylinositol specific phospholipase D(GPI-PLD) activity in patients of several liver disease.Method　Glycosylphosphatidylinositol (GPI) anchored placental alkaline phosphatase(PLAP) prepared by ourselves was used as a substrate.After partitioning by triton-X-114,the serum GPI-PLD activity was determined quantitatively and the data was treated by microware of SPSS 10.0.Results　On the basis of the percentage of GPI-anchored PLAP conversion,the sera GPI-PLD activities of total 172 patients,included 26 severe acute viral hepatitis as group A,29 liver cirrhosis as group B,32 chronic viral hepatitis as group C,55 mild acute viral hepatitis as group D,30 primary hepatocellular carcinoma as group E,were measured.As compared with 182 healthy presons as control group,the sera GPI-PLD activities of group A and B were significantly reduced;By contraries,the activities of group D and E were significantly raised.The sera GPI-PLD activities of group C compared with healthy control group were not significantly altered.However,when paired Q-test,the changes of serum GPI-PLD activity between all paired groups among this five groups were remarkable.Conclusions　The determination of sera GPI-PLD activities in patients can act as a biochemistry index for diagnosis of acute viral hepatitis,liver cirrhosis and primary hepatocellular carcinoma,as well as an auxiliary index for judgment of the curative effect and prognosis of liver diseases.