Aim To investigate the relationship between reactive hyperemia index(RHI) and blood homocysteine (Hcy) or carotid intima-media thickness (IMT) in patients with unstable angina pectoris(UAP). Methods A total of 245 consecutive patients taken coronary angiography(CAG)were enrolled in this study, and then divided, according to CAG, into normal group (n=65), SAP group (n=49) and UAP group (n=131). Vascular endothelial function was reviewed and RHI was calculated by using peripheral arterial tension (PAT) detection with Endo-PAT2000 (Itamar Medical Inc). IMT were measured with Color Doppler, and serum Hcy level was determined with enzymatic cycling assay. Results The RHI was significantly lower in UAP group than in the SAP group and normal group (UAP group＜SAP group＜normal group,P＜0.05);IMT was significantly higher in the UAP group than in SAP group or in normal group (UAP group＞SAP group＞normal group,P＜0.05);Hcy was significantly higher in UAP group than in normal group(P＜0.05); In UAP group,RHI was negatively correlated with serum Hcy level and carotid IMT (r=－0.494,r=－0.513,P＜0.01); Multiple linear regression analysis showed that it was independently correlated between IMT(X1), systolic pressure(X2), BMI(X3) and RHI(Y) in patients with UAP. Conclusion The serum Hcy level and IMT are positively associated with endothelial dysfunction(ED) in UAP patients, the serum Hcy level, IMT and RHI are correlated with the condition of patients with coronary heart disease.