Abstract： Objective To observe the protective effect of ulinastatin (UTI) on the intestinal barrier function of septic rats.Methods Septic rat model was established using Sprague-Dawley rats by cecal ligation and puncture (CLP) method.Thirty Sprague-Dawley rats were randomly divided into 3 groups (n =10 for each grop) : sham group, septic group and UTI group.All rats received intraperitoneal injections of 0.9％ saline (10 mL/kg) after and 8 h after surgery.In UTI group, UTI (10 × 104 U/kg in 10 mL/kg saline) was injected after and 8 h after surgery.Collect blood samples after 0, 8, 12 h after surgery to examine levels of procalcitonin (PCT), intestinal fatty acid binding protein (iFABP) and diamine oxidase (DAO) by enzyme-linked immunosorbent assay (ELISA) method.Rats were killed 12 h after surgery to collect intestine tissue samples.Pathological changes of intestine were observed under microscopy, and the expression of tight junction protein-1 (ZO-1) and occludin were analyzed by Western blot.Results In sham group, the mucosa structure was complete and the shape was normal, and villi stood neatly.In septic group, intestinal was expanded, intertinal mucosal was atrophic, villi were scanty.An inflammatory infiltrate with numerous nuetrophils was found in the mucosal.In UTI group, the level of severity was relatively slight.The relative optical density of Western blot images were decreased on ZO-1 and occludin in CLP and UTI groups, and decreased more in CLP group (F =43.15 and 52.23, P ＜ 0.05).At 0h after surgery, the plasma values of PCT, iFABP and DAO were similar in three groups (F =11.17, 22.45 and 13.58, P ＞ 0.05).At 8h and 12h after surgery, values of PCT, iFABP and DAO in septic and UTI groups were much higher than those in the sham group, and those in UTI group were also significantly higher than those in septic group (F8h=85.26, 44.59 and 101.47, F12h =59.44, 49.26 and 69.57, all P＜0.05).PCT, iFABP and DAO levels were first increased and then fell down in sham group, those in septic group were keeping increasing, and those in UTI group were first increased and then kept stable.Conclusion UTI shows protective effect to intestinal barrier function in rats with sepsis.