Abstract： Objective To study the Effect of acute peripancreatitc fluid collection and pancreatic necrosis to the prognosis of acute pancreatitis.Methods Retrospectively analyzing the prognostic effect of acute peripancreatitc fluid collection and pancreatic necrosis according to the early Computed-Tomograghy of 323 consecutive acute pancreatitis patients from Jan 2003 to Dec 2007,the end points are systemic inflammation response syndrome ( SIRS),pancreatic infection,and mortality.Results Within 5d after onset,97 of 323 cases (30%) presented with SIRS and lasted more than 2d,12 cases (3.7%) occurred pancreatic infection during middle or late phase,14 cases died,the mortality is 4.3%.141 of 323 cases (43.7%) who had acute peripancreatic fluid collection presented with SIRS,acute peripancreatic fluid collection correlated significantly with the occurrence of SIRS,P ＜ 0.05.227 cases (277/323,85.8%) had no pancreatic necrosis,no pancreatic infection occurred,46 cases (46/323,14.2% )had pancreatic necrosis,pancreatic necrosis correlated significantly with pancreatic infection,P ＜ 0.05.Conclusions Acute poripancreafic fluid collection and pancreatic necrosis had different prognostic effect to acute pancreatitis.Acute peripancreatic fluid collection correlated well with the occurrence of SIRS during the early phase;Pancreatic necrosis may be infected during middle or late phase of acute pancreatitis,more extent of pancreatic necrosis,more possible that pancreatic infection will occur.