Abstract Objective To study the effect of Edaravone (ED) on TGF-β1 of cardio- pulmonary bypass (CPB)-induced lung injury. Methods 30 adult hybrid health dogs, were randomly divided into three groups(n=10): groupC(received normal saline after CPB), groupE1 (receive ED given intravenously after CPB started), groupE2(receive ED before CPB started). Lung specimens were obtained before CPB(T0)、at 30min following CPB(T1)、15min after CPB(T2)、30 min after CPB(T3)、60 min after CPB(T4)in all groups. The expression of TGF-β1, superoxide dismutase activity( SOD) lung tissue was detected at above-mentioned time points. and the histological appearance of lung under microscope in 3 groups were examined. Blood samples were collected from femoral artery for the monitoring of Respiratory index（RI）at T0 ,T2, T3. and then to understand the effects of ED on pulmonary TGF-β1 of CPB-induced acute lung injury. Results No significant differences were found in the levels of RI in the three groups before CPB (P＞0.05). However, RI were increased gradually after CPB(P<0.05), They was increased significantly greater in group c than in groupE1, E2 at T2,T3 (P<0.05). the RI were significantly lower in group E1 than in group E2 at T2,T3 (P<0.05); No significant differences were found in the content in lung tissu SOD activity in the three groups before CPB (P＞0.05). They were gradually decreased after CPB(P<0.05), they were still significantly lower in group E1 and groupE2 than those in group C at T1,T2 ,T3,T4 (P<0.05); by electromicroscop examination, lung inflammatory to chang, However These changes were markedly alleviated in group E2 and group E1 ; expression of TGF-β1: The expression of TGF-β1 was ocassionally detected at T0 and was increased in three groups with the time of CPB, but it was lower in group E1 than that in group E2 and group C. Conclusion The expression of TGF-β1 significantly increased after CPB. ED could can clearance down-regulate expression of TGF-β1, to improve RI，may provide better protection against the injuries. The protetive effect of is better with in in group E1 than in group E2.