Abstract: Objective To study the effect of ambroxol hydrochloride on hyperoxia-induced lung injury in adult rats. Methods Forty-eight male Sprague-Dawley（SD） adult rats were randomly divided into control group（0h group）,and 24,48,72,96h and ambroxol hydrochloride intraperitoneal（ABX） groups,8 in each group.Rats in control group received room air,those in 24,48,72 and 96h groups received 100% O2 in hyperbaric oxygen chamber,and ABX group received ABX injection（30mg/kg per day）.Carotid blood gas was analyzed and cytokine level in bronchoalveolar lavage fluid（BALF） was measured.Expression level of tumor necrosis factor-α（TNF-α）,IL-1β and IL-6 were measured respectively.Activity of enzyme and expression of Bax and Bcl-2 in lungs were detected. Results The oxygenation index decreased gradually with the increasing exposure time to oxygen and reached its minimum at 96h.The expression level of TNF-α and IL-1β in serum and BALF increased gradually and reached its peak at 48h,and then decreased gradually.The expression level of IL-6 reached its maximum at 72h.The expression of Bax was gradually increased while that of Bcl-2 in lungs was gradually decreased.The oxygenation index,expression levels of TNF-α,IL-1β,IL-6 and Bax in serum and BALF were significantly lower while the expression level of Bcl-2 in lungs was significantly higher in ABX group than in 96h group（P＜0.01）. Conclusion Ambroxol hydrochloride can attenuate hyperoxia-induced lung injury in adult rats through its anti-inflammatory,anti-oxidant and anti-apoptosis effects.