Abstract： Objective To study effects of abnormal glucose metabolism on the endothelial function in brachial artery. Methods We measured endotheliundependent and endotheliumindependent brachial artery dilatation in patients with impaired glucose tolerance (IGT,n=39),T2DM(n=47)and NGT(n=44) by using high resolution ultrasound. Results The endothelial dilatation functions (EDF) were damaged in IGT and T2DM groups,and were more damaged in T2DM than in NGT group(P＜0.01）.The FPG,HbA1c and LDLC were elevated in IGT and T2DM as compared with NGT,and were negatively associated with EDF,HDL-C was positively correlated with EDF. Conclusions Abnormal glucose metabolism damages vascular endothelial dilatation function.