Abstract Background/Introduction Angiotensin-converting enzyme (ACE) 2 is the homologue of ACE, and the local up-regulation of ACE2 expression associates to antiatherosclerosis. ACE2 hydrolyzes the angiogensin II, which related to impair of endothelial progenitor cell (EPC) function. EPCs maintain the integrity of vascular endothelium in case of damage. Decreased number of EPCs associate thrombosis. Purpose To investigate the circulating ACE2 and the link to EPC in CAD patients. Methods Data from 650 patients with stable angina pectoris requiring invasive coronary angiography were enrolled. They were divided into two groups according to the median value of ACE2. Two interventional cardiologists diagnosed obstructive CAD by angiography review. Demographic characteristics and clinical outcomes were compared between groups. Results In all subjects (median age 67 years, male=66.9%), a higher ACE2 level indicates elder, higher prevalence of hypertension, diabetes mellitus and chronic kidney disease. Significant EPC elevation when CAD numbers increased in higher ACE2 group (SVD vs. DVD vs. MVD = 0.005 vs. 0.006 vs. 0.007, p value=0.044). In multivariate analysis, higher ACE2 is positively correlated to triple vessel disease (TVD vs. no CAD, adjusted odds ratio=1.627, 95% CI 1.026-2.579). Conclusions Our data demonstrated higher circulation ACE2 links to EPCs in CAD patients.