Objective To investigate Interleukin 6(IL-6),superoxide dismutase (SOD),malondialdehyde (MDA) in lung tissues of a rat acute pulmonary edema model induced by acute hypoxia. Methods 50 adult Wistar rats were randomly divided into group A (normal),B (acute pulmonary edema,hypoxia for 24 h),C (acute pulmonary edema,hypoxia for 48h),D(acute pulmonary edema,hypoxia for 72 h) and E (dexamethasone treatment,hypoxia for 72h). The model of acute pulmonary edema was established by intraperitoneal injection with 6% ammonium chloride. In group E, dexamethasone (6mg/kg) was injected in tail vein following intraperitoneal injection of 6% ammonium chloride. The rats were killed 24(group B), 48 (C) and 72 hours(D&E) later. Plasma was isolated and lungs were removed. MDA,SOD in lung tissues and IL-6 in plasma were analyzed by ELISA. Results The wet weight of lung tissues were significantly increased in group B, C and D compared to group A(P<0.05). The lung tissues of group A had no obvious congestion and edema,and the morphology of lung tissues was normal(P>0.05). Pulmonary edema,interstitial spaces and alveolar filled fluid can be seen in group B,C,D and transparent membrane formed within alveoli. The lung tissue congestion and edema in group D were the most obvious(P<0.05). The above changes obviously improved in group E. Compared with group A,MDA,IL-6 increased and SOD decreased in lung tissues of group C and D. Compared with group D, MDA was decreased and SOD was increased in lung tissues of group E and IL-6 was also decreased significantly in plasma(P<0.05). Conclusion The occurrence of acute pulmonary edema related to oxidative stress and decreased antioxidant capacity. Increased free radical is an important mechanism of pulmonary edema. SOD,MDA and IL-6 in the lung tissue may be indexes for the prognosis.