Objective To investigate the effects of emodin on inducible nitric oxide synthase (iNOS) expression of pancreatic tissue, serum leptin and intestinal permeability in rats with acute pancreatitis(AP) and the relative mechanism. Methods Sixty adult SD rats were randomly divided into three groups: sham operation group, AP group, and emodin treatment group, with 20 in each group. The expressions of iNOS and NO in pancreatic tissue were measured. Blood amylase(AMY) and serum content of leptin were detected. Intestinal permeability was measured by albumin clearance(AC) of 125I-labeled rat serum albumin. The histopathologic changes of pancreas and ileum were observed. Results The blood AMY, plasma content of leptin, cumulative 125I-labeled serum albumin index and the levels of iNOS and NO in pancreatic tissue were significantly higher in AP group and emodin treatment group than in sham operation group(P＜0.05). Compared with AP group, in emodin treatment group, the levels of iNOS and NO in pancreatic tissue, the blood AMY and cumulative 125I-labeled serum albumin index were significantly decreased(P＜0.05); the serum content of leptin was increased; the pathological changes of pancreas and ileum were significantly alleviated(P＜0.05). Conclusion The increase of intestinal permeability in rats with AP may be induced by overexpression of NO via action of iNOS. Emodin is effective in the increase of the serum leptin and the decrease of iNOS. Emodin has certain preventive and therapeutic effects on bowel wall permeability decrease in AP rats.