Objective To explore the severity of acute pancreatitis induced by intraperitoneal injection of 50μg/kg caerulein at different doses in mice. Methods Acute pancreatitis(AP)was induced by intraperitoneal infection of 50μg/kg caerulein at 3,6,9,12times, respectively.We evaluated the severity of AP biochemically and morphologically. Results Conventional doses of caerulein(50μg/kg) were injected with 3, 6, 9, 12 times, the level of serum amylase in experimental group were significantly higher than that in control group(P< 0.05), peaked in the 9 times[(25 966.67±3 787.02)U/L]; pancreatic water content in the experimental group was significantly higher than that in control group(P< 0.05), peaked in the 6 times[(81.13±1.03)%]; pancreatic tissue hematoxylin and eosin(HE)staining showed that pancreas was slightly edema and infiltration of inflammatory cells at 3 times, which showed a large amount of neutrophil infiltration and obvious edema at the 6 times, and pancreatic leaflet margin appeared a small amount necrosis at the 9 times, and the acinar necrosis foci could be seen in large range an the 12 times(histopathological score 8.20±0.84), the microscope exhibited altered necrotizing pancreatitis. Conclusion Conventional caerulein doses(50μg/kg)may induce acute edematous pancreatitis by 6 times of intraperitoneal injection in mice, and 12 times may induce acute necrotizing pancreatitis. Key words: Acute pancreatitis; Caerulein; Model, animal