Objective;To investigate the pathogentic factor of severe acute pancreatitis(SAP)associated lung injury and the protective function of octreotide combined with alinastatin on SAPassociated lung injury in rats. Methods;Eighty SD rats were randomly divided into 5 groups. Sham operative （S）group, SAP group, octreotide（O）group, ulinastatin （U）group and octreotide + ulinastatin （O+U）group, and each group was divided into 6h,12h subgroups. After AP models were induced, the serum concentration of amylase(AMY),tumor necrosis factorα(TNFα), malondiadehyde (MDA), and the concentration of myeloperoxidase(MPO) in lung tissue were determined; and the pancreas and lung pathology were graded, the changes of the abovementioned indexes after using octreotide and ulinastatin were compared.Results;（1）Compared to SAP group , AMY, TNFα,MDA, MPO, and pancreas pathology score were decreased significantly in each of the 3 therapy groups during the same period;and at 12h, in O+U subgroup,lung pathology score also decreased compared to SAP group(P<0.05 ).（2）Compared to O group, in O+U group, MPO significantly decreased(P<0.05);and compared to U group, MDA also had significant decline(P<0.05 ).(3)TNFα significantly decrease in SAP group at 12h compared to 6h.（4）There was a positive correlation between AMY, TNFα,MDA,and MPO with pancreas and lung tissue pathology scores (r=0.343~0.781，P<0.01). Conclusions;(1)TNFα,MDA，and MPO are important pathogenetic factors for SAPassociated lung injury. (2)Octreotide and ulinastatin can decrease the degree of SAPassociated lung injury,and a better effect could resulte from combination of octreotide with ulinastatin.