Aim To investigate the association between expression and activity of matrix metalloproteinase-9(MMP-9) and type 2 diabetic macroangiopathy and explain the mechanism of anti-atherosclerosis effect of Rosiglitazone. Methods Type 2 diabetic rat model was established by high-fat diet and a low dose of STZ. The activity of MMP-9 in arterial wall was observed by SDS-PAGE zymography. The MMP-9 mRNA expression in arterial wall was observed by RT-PCR.Meanwhile the changes of MMP-9 expression and activity were observed after Rosiglitazone treatment for 4,8 and 12 weeks. Results The activity of MMP-9 in model rats was 1.27 times as high as that of control rats,with the prolongaton of diabetes duration and the development of macroangiopathy,its activity increased progressively and was 1.69,2.25 and 2.92 times of control rats,respectively,at week 4,8 and 12 after DM.MMP-9 mRNA in model rats was 1.15,1.30,1.45 and 1.99 times higher than that of control rats at week 0,4,8 and 12 after DM.MMP-9 activity was dropped by 11.56%,37.73% and 48.60% in Rosiglitazone group after treatment for 4,8 and 12 weeks.MMP-9 mRNA was dropped by 26.80%,27.16% and 46.46% in Rosiglitazone group after treatment for 4,8 and 12 weeks. Conclusions The changes of MMP-9 expression and activity occured during the development of type 2 diabetic macroangiopathy.The mechanisms of anti-atherosclerosis effect of Rosiglitazone might be related to inhibiting MMP-9 expression and activity.