Objective To investigate the changes of NF-κB，MMP-2 and TIMP-2 protein and its mRNA in the rats with acute lung injury ( ALI) caused by lipopolysaccharide ( LPS) . Methods Twenty male Wistar rats were randomly divided into two groups: normal control group，LPS model group. Each group had two subgroups，4 hours and 8 hours after LPS were injected. The ALI model was established by intravenous injection of LPS (10 mg / kg) through a tailvein. Then the white blood cell (WBC) in blood and the protein content in bronchial alveolar lavage fluid( BALF) were measured，the expressions of nuclear factor-κB ( NF-κB ) ，matrix metalloproteinase-2 ( MMP-2 ) and tissue inhibitor of matrix metalloproteinases ( TIMP-2) protein in pulmonary tissues were measured by immunohistochemistry ABC ，the expression NF-κB ，MMP-2 and TIMP-2mRNA were measured by real-time fluorescent polymerase chain reaction( PCR) ，while the histopathology of the lung injury was observed by light microscope. Results Compared with normal group，the expression of NF-κB and MMP-2 protien dyeing positive rate of area and its mRNA in LPS model group were obviously increased at 4 hours and 8 hours (P < 0. 01) ，and the expression of TIMP-2 protein dyeing positive rate of area and its mRNA at 4 hours and 8 hours were obviously decreased in LPS model group (P < 0. 05or P < 0. 01) . Light microscope observation indicated that there were pulmonary hemorrhage and necrosis in model group. Conclusion The increasing of expression NF-κB and MMP-2 protein and its mRNA and the decreasing of expression TIMP-2 protein and its mRNA may be the mechanism of ALI caused by LPS.