Abstract: Objective: To investigate the changes of serum angiotensin converting enzyme（ACE）activity and pulmonary endothelin-1（ET-1） content in rabbits with acute lung injury（ALI） induced by endotoxin and the effects of meloxicam,so as to explore the protective mechanism of meloxicam.Methods: Twenty four Japanese flap-eared white rabbits were randomly assigned to three groups : control group,endotoxin-treated group and meloxicam-treated group.ALI models of rabbits were replicated with intravascular endotoxin injection（700 μg/kg weight）,meloxicam（2.5 mg/kg weight） was intravascularly injected in treatment group.We measured serum ACE activity and pulmonary ET-1 content in every group.Results: In endotoxin-treated group,serum ACE activity increased at 0.5h,and reached a peak at 1h.In meloxicam-treated group,ACE activity in serum also increased,while serum ACE activity was significantly lower than that in endotoxin-treated group.In endotoxin-treated group,the levels of ET-1 in lung tissue were significantly higher than those in control group（P＜0.01）.In meloxicam-treated group,the levels of ET-1 in lung tissue were significantly lower than those in endotoxin-treated group（P＜0.01）.Conclusion: Meloxicam can inhibit serum ACE activity and down-regulate the levels of ET in lung tissue,which posseses some protective effects on ALI induced by endotoxin in rabbits.