Aim To study the effects of aspirin and clopidogrel on expression of matrix metalloproteinase-1(MMP-1) and stability of plaque in aortic artery of atherosclerostic rabbits. Methods Forty-nine rabbits were divided into normal control group,model group,aspirin group,clopidogrel group and combination(aspirin+clopidogrel) group.Atherosclerostic model in aortic artery induced by high lipid diet chow and immunity injury were built in the last four groups.The positive percentage of macrophage cells and smooth muscle cells in the plaque were analyzed by immunohistochemistry.Expression of MMP-1 in aortic artery was measured by Western blot. Results Aspirin and clopidogrel significantly decreased the positive percentage of macrophage cells,and increased the positive percentage of smooth muscle cells in aortic vascular lesions(p<0.05 or 0.01).The localization of the expression of MMP-1 was in concordance with macrophage cells region.Compared with normal controls,the amounts of MMP-1 increased by 562%,217%,211% and 178% in model group,aspirin group,clopidogrel group and their combination,respectively(p<0.05). Conclusions Aspirin and clopidogrel can reduce expression of MMP-1 and change the compounds of plaques.These effects may increase the stability of plaques.