Objective To investigate the effects of simvastatin on lung tissue in septic rats by observing the protein expression of nuclear factor kappa B ( NF-κB) and pathologic changes in lung tissue at different time points. Methods 90 healthy male Sprague-Dawley rats were randomly divided into three groups ( n =30 in each group) . All the rats received administration by caudal vein and capacity volume is 2 mL. The rats in the control group were treated with saline ( 2 mL) . The rats in the LPS group were treated with LPS ( 5 mg/kg ) . The rats in the simvastatin group were treated with LPS ( 5 mg/kg) and simvastatin ( 20 mg/kg) . Six rats in each group were killed randomly at 2, 4, 6, and 12 hours after the injection, and the right middle lobe of lung was taken out. Pathological changes of lung tissue wee investigated under light microscope. The expression of NF-κB in lung tissue was determined by immunohistochemistry ( IHC) method. Results Microscopic studies showed that there were not pathological changes in the lung tissue of rats in the control group. While in the LPS group, the alveolar spaces were narrowed and the alveolar wall were thickened. Furthermore, severe interstitial edema of lung and proliferation of epithelial cells were observed. In the simvastatin group, the degree of the infiltration of leukocytes and the lung interstitial edema were less severe than those in the simvastatin group. In the control group, the expression of NF-κB protein in most of lung tissue was negative. In the LPS group, the expression of NF-κB protein was detected at 2h, andreached the peak at 6h, then decreased at 12h. In the Simvastatin group, the NF-κB expression was significantly lower than that in the LPS group at all time points ( P lt; 0. 01) . Conclusion Simvastatin can ameliorate pathological lesions and decrease expression of NF-κB in lung tissue of septic rats.