Abstract: Objective:this study was to investigate the role of lung in multiple organ failure in aged rats.Methods:E. Coli Endotoxin was injected intravenously to aged rats to produce MOF Model, the immune and biochemical parameters and pathological change were observed dynamically in 1、2、6、12 and 24 hours subgroup afer endotoxin injection.Results:lung injury and pulmonary failure occured firest at 2 hours after endotexin injection, Serum ACE decresed and C5a increased. The Concentrations of TNF, SOD and LPO Markedly elevated in the lung tissues. Under light microscopy the interstitial and intraalveolar edema and hemerrhage, leucocyte infiltration and aggregation in the lung were more severe in 2h.Conclusion:（1）The pulmonary failure occurred first during MOF in aged rats. （2）The large amounts of inflammatory Mediators produced in the lung and the hypoxemia after pulmonary failure may contributed to the occurrence of MOFE.