目的　本研究旨在观察西拉普利对大鼠缺氧性肺动脉高压血管内皮的保护作用机制。　方法　观察大鼠缺氧性肺动脉高压的血液动力学的变化及循环内皮细胞、血管紧张素转换酶、脂质过氧化物的变化。　结果　缺氧性肺动脉高压时脂质过氧化物产生增加 ,血管紧张素转换酶活性降低 ,循环内皮细胞数量增加 ( P<0 .0 1) ;西拉普利治疗后脂质过氧化物降低 ,循环内皮细胞数量减少 ( P<0 .0 1)。　结论　西拉普利抑制脂质过氧化等对血管内皮细胞有保护作用。 Objective This study aimed to observe the mechanism of cilazapril protective effect on vascular endothelial cells of hypoxic pulmonary hypertension in rats. Methods The changes of hemodynamics and the changes of circulating endothelial cells, angiotensin converting enzyme and lipid peroxides in rats with hypoxic pulmonary hypertension were observed. Results Hypoxic pulmonary hypertension increased lipid peroxidation, reduced angiotensin converting enzyme activity, and increased circulating endothelial cells (P <0.01). After treatment with cilazapril, lipid peroxides decreased, The number of circulating endothelial cells decreased (P <0.01). Conclusion Cilazapril inhibits lipid peroxidation and other protective effects on vascular endothelial cells.