Objective To investigate the possible role of ulinastatin(UTI) in f lipopolysacccharide (LPS)-induced acute lung injury(ALI).Methods Thirty male SD rats were randomly divided into three groups，ie.a normal control group，a LPS group and a LPS plus UTI group.The rats were injected with 1 mL of normal saline via caudal vein in the control group，with LPS 5 mg/kg via caudal vein in the LPS group，and with UTI 100000 U/kg shortly after injection with LPS in the LPS plus UTI group.The rats were sacrificed 4 h after the injection.Lung wet/dry weight ratio was measured.IL-18 level in serum and lung tissue was determined by ELISA and the expression of NF-κB in lung tissue was determined by immunohistochemistry.Pathological changes of rats’ lung were observed by optical and electron microscope.Results Compared with the control group，IL-18 level in serum and NF-κB expression in lung tissue were significantly higher in the LPS group(Plt;0.01).The IL-8 level was somewhat elevated in the LPS+UTI group but with no significant difference from that in control group was found (Pgt;0.05).The lung inflammation in the LPS+UTI group was milder than that in the LPS rats.Conclusion UTI can alleviate LPS-induced inflammatory reaction and lung injury in rat model.