Objective To establish a stable and reliable lung injury model caused by severe acute pancreatitis（SAP）in rats， which is helpful to study the acute lung injury （ALI）and acute respiratory distress syndrome （ARDS） induced by SAP.Methods Sixty Sprague-Dawley rats were randomized into ligature group （n=20）， traditional group （n=20），and sham operation group （n=20）. SAP model was established through retrograde injection of 5% taurocholic acid. After injection， the pancreatic duct of rats was ligated in ligature group， but not in traditional group. The lung damage and edema at 24 h after operaton and natural course of rats were observed.Results The ALI model of rats induced by SAP was established successfully in ligature group. The rats died of acute respiratory failure within 48 h in ligature group， the mortality was significantly higher than that in traditional group （100% vs.20%），P＜0.05. Pleural effusion occurred in four rats in ligature group， while no pleural effusion was found in rats in other two groups. The volume of ascites of rats in ligature group was （21.15±5.33） ml， which was more than that in traditional group 〔（7.75±2.66） ml〕，P＜0.05， while no ascites was found in rats in sham operation group. The level of serum amylase of rats in ligature group was （2 470.70±399.73） U/L，which was significantly higher than that in traditional group 〔（1 528.40±289.54） U/L〕 and sham operation group 〔（831.10±93.26） U/L〕，P＜0.001. The level of serum albumin of rats in ligature group was （6.90±1.66）g/L， which was significantly lower than that in traditional group 〔（13.10±0.99） g/L〕 and sham operation group 〔（16.20±0.92） g/L〕，P＜0.001.The lung wet-to-dry weight ratio （W/D） of rats in ligature group was 6.50±0.23， which was greater than that in traditional group （4.92±0.18） and sham operation group （4.61±0.16）， P＜0.001. The score of lung histopathologic of rats in ligature group was 29.25±1.07， which was significantly higher than that in traditional group （12.65±1.98） and sham operation group （0），P＜0.001. The score of pancreas histopathologic of rats in ligature group was 15.95±0.15，which was significantly higher than that in traditional group （13.75±0.66） and sham operation group （0.13±0.29），P＜0.001. Under transmission electron microscope， basement membrane of pulmonary capillary of rats in ligation group was destructive， the nuclei was dissolved， endothelial pinocytotic vesicles was functional active， and tight junctions between capillary endothelial cells were blurred and even ruptured. Moreover， tight junctions between alveolar epithelial cells were destructive. Pathological changes of lung ultrastructure of rats in ligation group were more severe than that in traditional group， while no pathological change of lung ultrastructure was observed in rats in sham operation group. Conclusions Injury process and pathogenesis of ALI or ARDS clinically caused by acute gallstone pancreatitis can be reproduced in this animal model， which is suitable to explore the related mechanisms of ALI caused by SAP and provides good animal model for the study of ALI caused by SAP.