Abstract: Objective: To study the changes of von Willebrand Factor（vWF） come from endothelial in blood plasma in endotoxin（ET）-induced acute lung injury（ALI） in rabbits,to observe the interference effects of chloroquine on vWF to reveal the principle of endothelial cell damage in ALI,and to find out effective therapeutic method for ALI in clinic.Methods: 24 rabbits were randomly assigned to three groups: group A（control group）,group B（ET group）,and group C（ET and chloroquine group）.ALI was induced by intravascular injection of ET（600 μg/kg）.The rabbits of group C were injected by chloroquine after ET injection.The vWF、 malondialdehyde（MDA）、superoxide dismutase（SOD） and PaO₂ were measured before injection and 0.5 h,1 h,2 h,4 h after injection in every group.The results were analyzed.Results: VWF and MDA were higher in group B than that in group A.But SOD in group B was lower than that in group A.The results of group C were similar with group B but the extents of changes were lower than that in group B.The differences of every group were significant.Conclusion: The change of vWF is one of the identifications in ALI.Chloroquine injection can depress the action of vWF.So chlorquine has protective effect to endothelial cell in ALI.