Aim To observe the effect of vitamin C on blood lipid and aorta expreeion of heparin sulfate proteoglycan protein (HSPG) in streptozotocin-induced diabetic rats. Methods Diabetic nephropathy rats were induced by intraperitoneal injection of STZ. Rats were allocated to normal control group, model group,and vitamin C group for 16 weeks. During and after the treatment, during and after the treatment, Its general state, blood suger (BS), triglyceride (TG), total cholesterol (TC), low density lipoprotein (LDLC), high density lipoprotein (HDLC), glycosylated hemoglobin (HbA1c) and glycosylated low density lipoprotein (G-LDL) Alteration of tissue morphology via HE staining was observed after the aorta was taken out from the rats executed by narcosis; heparin sulfate proteoglycan protein, were determined by immunohistochemistoche. Results (1) Diabetes mellitus and aortalesion occurred in the four model groups. (2)Vitamin C have no effect on the blood gloucoselevels,while they could improve the general state, improve the general state, decreasetriglyceride (p<0.05), serum cholesterol (p<0.05), low density lipoprotein (p<0.05), glycosylated hemoglobin (p<0.05), and glycated low density lipoprotein (p<0.05), increase high density lipoprotein (p<0.05), Theexpreeion of HSPG in the kidney were significantly inhibited (p<0.05) at the same time. Conclusion Vitamin C have no effect in decreasing the blood sugar level but have a certain in preventing renal.