Objective To investigate the effect of MMP-9 on severe acute pancreatitis(SAP) associated with lung injury,and the preventive function of MMP-9 inhibitor (BB-94) in SAP associated with lung injury in rats. Methods SD rats were randomly divided into three groups: Shamed-operated groups (control groups,n=10);SAP groups (n=14);SAP with MMP-9 inhibitor preconditioning groups (BB-94 group,n=15). The samples for test of the wet weigh index of lung,serum amylase level,white cell count,the number of cells and protein in bronchoalveolus lavage fluid,histologic scoring of lung injury and MMP-9 in lung were detected 24 hours after SAP models were set up.Results The parameters mentioned above in SAP group were significant higher than those in controll group and BB-94 group (P