Objective To investigate the role of endothelin（ET） in lung injury during cardiopulmonary bypass （CPB） and study the possible mechanism of ET-mediated lung injury and the protective effect of ferulic acid（FA） during the procedure. Methods Twelve dogs were randomly divided into 2 groups and models of CPB with pulmonary perfusion were established by perfusion of 4 C FA solution through proximal pulmonary artery in the experiment group while control group only received 4 C crystal cardiac arrest solution without pulmonary perfusion. Changes in the content of ET, NO, malonaldehyde （MDA）, dry to wet （D/W） in lung tissue and lung function- related indices PaO2/FiO2, airway pressure （AWP）, pulmonary vascular resistance （PVR）, lung compliance before and after CPB in both groups were measured respectively. Results ET content increased after CPB in control group （P〈0. 05） ,while experiment group had a lower level of ET than that of control group （P〈0.05）; D/W, MDA levels in experiment group decreased （P〈0. 05）, but NO content increased （P〈0. 05） as compared with control group. After pulmonary perfusion with FA, PaO2/FiO2 and lung compliance values in experiment group were higher than those of control group （P〈0.05）,AWP, PVR values lowered accordingly（P〈0. 05）. Lung injury was less severe in the experiment group. Conclusion ET is involved in pathogenesis of lung injury during CPB, FA can effectively reduce lung injury and improve lung function thus having a good protective effect on the lung.