Abstract： Objective To explore the relationships between the hyperglycemia and apoptosis of coronary artery endothelial cells as well as expression of the apoptotic gene of diabetic rats. Methods The STZ-induced Wistar diabetic rats were divided into three groups: diabetic rats without （treatment;） the insulin-treated diabetic rats; and the control. At 0 and 16 weeks, the coronary artery outlets of the rats were collected as experimental material to examine apoptosis by using TUNEL, electromicroscopic changes and related gene expression with immunohistochemistry method. Meanwhile, the blood samples were collected to examine levels of TG,TC,HDL, LDL. Results The body weights were decreased in treated DM （205±23 vs 243±28 gram in control） and untreated DM （（169±25） vs 243±28 gram in control） （P<0.05）. HbA1c levels were higher in treated MD （4.0±0.2% vs 3.4±0.3% in control） and untreated DM （8.2±0.4% vs 3.4±0.3% vs control） （P<0.05） significantly. The numbers of endothelial cell apoptosis were increased in untreated DM （22.8±6.9 vs 5.4±2.4% in control P<0.05） and in no significant change in treated DM （4.9±2.0% vs 5.4±2.4% in control, P>0.05）. Compared with control, the untreated DM had increased fas expression （62±12% vs 26±7%,P<0.05）, and decreased bcl-2 expression （18±5% vs 41±10%, P<0.05） while the treated DM had the same levels of fas and bcl-2 expression （28±8% vs 26±7% and 40±10% vs 41±10% separately, all P>0.05） as those of control. Conclusions Hyperglycemia is a apoptotic factor of vascular endothelial cell of diabetic rats; the apoptosis is correlated with up-regulation of expression of fas gene as well as down-regulation of expression of bcl-2 gene in diabetic rats.