Objective;To investigate the effect of plateletactivating factor acetylhydrolase(PAFAH) on severeacute pancreatitis(SAP). Methods;Fortyfive male Wistar rats were randomly divided into three groups(n=15 in each group),including group A(sham operation group),group B(SAP group) and group C(PAFAH treated group).PAFAH(5mg/kg) was infused through the dorsal artery of penis after 1 hour and 24 hours of establishing the model in group C.Fortyeight hours after animal models were established,the levels of maleic dialdehyde(MDA),thromboxane B2(TXB2),prostaglandin I2(PGI2),TXB2/PGI2,plateletactivating factor(PAF),endotoxin,tumor necrosis factor(TNFα) in serum,and the activity of myeloperoxidase(MPO) in lung tissue were examined in each group.The pancreas was scored on the basis of pathological changes. Results;Compared with group B, the levels of MDA, TXB2,TXB2/PGI2, PAF,endotoxin,TNFα in serum, and MPO activity in lung tissue and the pathological scores of pancreas were significantlylower in group C(P<0.05). There was no obvious difference in the level of PGI2 between group B and group C （P>0.05）. Conclusions;PAF plays a critical role during the course of SAP.Administrationof PAFAH can hydrolyze PAF,improve pancreatic microcirculatory dysfunction,suppress systemicinflammatory reaction,relieve pancreatitisassociated intestinal tract injury and lung injury and markedlyameliorate the state of SAP.