The ultrastructural changes of aorta in adult Wistar rats with streptozotocin(SZ) induced non-insulin-dependent diabetes mellitus were observed.Meanwhile, plasma lipid,lipid peroxides(LPO) and supperoxide dismutase(SOD) levels were measured.The results showed that both diabetic group and fat group had ultrastructural pathologic changes in their wall and the situation in diabetic group is severe than in fat group and the differences in subendothelial depth,numbers of layers of smooth muscle cells in intima and points scored for damage in intima were very significant(p< 0. 01). The plasma triglycerides, total cholesterol and low density lipoprotein cholesterol levels were increased(p< 0. 01), but high density lipoprotein cholesterol/low density lipoprotein cholesterol was decreased(p<0. 01)in fat group and diabetic group. The plasma LPO levels in diabetic group and fat group were increased(p<0. 01), the plasma SOD levels in diabetic group was decreased but increased in fat group(at the forth week, p<0.05; at the tenth week,p<0. 01). The results above indicate that the experimental SZ-induced non-insulin-dependent diabetes mellitus rats rats have the early ultrastructural pathologic changes in aorta wall,which would be associated with the increase of LPO, decrease of SOD and the disorders of lipid metabolism.