In order to observe activity of tumor necrosis factor (TNF) in the serum, pancreatic histopathological damage, as well as their relationships in acute necrotizing pancreatitis (ANP), thirty five SD rats were randomly divided into 7 groups according to their sampling time with 5 in each group. ANP was induced by retrograde infusion of 5% sodium taurocholate through biliopancreatic duct in 6 experimental groups (Group B1～B6).Blood and pancreatic tissue samples were obtained at hour 0,0.5,2,4,6 or 8 respectively when the animals were sacrificed.Results showed that serum level of TNF activity rose significantly in Group B2,and reached the maximal value in Group B4.The pancreatic histopathological damage in ANP rats was getting worse along with time. Serum TNF activity had close relation to pancreatic histopathological score (r=0.63, Ｐ＜0.01),suggesting that serum TNF may play an important role in the process of deterioration of pancreatic tissue damage during ANP.