Abstract： Objective To investigate effects of hyperbaric oxygen on endotoxemia and its inflammatory mediators as well as pulmonary pathology in rabbits. Methods Thirty-six healthy New Zealand rabbits were equally divided into two groups (n = 18 ),the HBO group and the control group. The animal model of endotoxemia was developed with an injection of 20 μg of lipopolysaccharide (LPS) through the ear edge vein.The HBO group was given HBO therapy twice,60 minutes each time. Two hours after an injection of LPS ( after the first session of HBO therapy) and 4-hours after an injection of LPS ( after the second session of HBO therapy) respectively,blood samples were collected from ear arteriae of both groups for measurement of TNF-α,IL-8,CRP,TXB2 ,6-keto-PGFlα,arterial blood gas and finally pulmonary pathological examination. Results When compared with the control group,HBO therapy could obviously improve the oxygen partial pressure in arterial blood for endotoxemia,significantly decrease serum concentrations of TNF-α,IL-8,TXB2 (P ＜ 0.05 ),elevate concentrations of serum CRP and 6-keto-PGF1α (P ＜ 0.05 ) and alleviate infiltration of polymorphocytes (PMN) and edema. Conclusions HBO therapy could significant improve symptoms derived from endotoxemia,correct imbalance of inflammatory mediators and reduce pulmonary pathologic lesion.