Abstract: objective: To study the pathogenesis of acute lung injury （ALI） of rabbits induced by intravascular injection of endotoxin （ET）, as well as the role of the activation of phospholipase A 2（PLA 2）. Methods: Rabbits were randomly assigned to three groups: control group, ET group, and chloroquine group（treated by both ET and chloroquine）. Acute lung injury was induced by intravascular injection of ET （500 μg/kg）. The PLA 2 activity in serum and pulmonary tissue and the arterial gas analyses were measured before and after ET injection in three groups. Electron microscope and light microscope were used to observe the pathological damages in the pulmonary tissue. The protective effects of chloroquine were both observed and analyzed. Results: Compared with saline controls, rabbits treated with ET showed the early damage of ALI, such as the decrease of PaO 2, pulmonary edema, endothelial and epithelial cells injury. The PLA 2 activity significantly increased in ET group compared with the basal activity and control group （P＜0.01）. In chloroquine group, the PLA 2 activity was higher than control group （P＜0.01）, but lower than ET group （P＜0.05）. Conclusion: Intravascular injection of ET induced ALI in rabbits. PLA 2 activation played an important role in the pathogenesis of ALI. The inhibitor of PLA 2, chloroquine, reduced the hypoxia and PLA 2 activation caused by ET, therefore could alleviate the early damages in lung tissue induced by ET injection.