Background: Coronary artery disease (CAD) is currently the leading cause of death among people around the world. The main cause of CAD is atherosclerosis or vascular arrest. In the etiology of this disease, various factors, including genetic factors, are involved. In this study, the effect of angiotensin converting enzyme (ACE) as a risk factor was evaluated. Increasing ACE activity by enhancing the synthesis of angiotensin II is likely to contribute to the risk of atherosclerosis. Materials and Methods: In this case-control study, 145 healthy individuals and 154 patients were selected from among patients referred to the Shahid Madani Hospital. Absorption of atherosclerosis in healthy individuals and atherosclerosis in patients with standardized angiography was confirmed. The case and control groups were matched for age and gender. A 5 ml sample of blood was taken from each person, and the serum was isolated. ACE activity was measured using HHL substrate and HPLC techniques. Results: The results showed that the level of ACE activity in patients with atherosclerosis was higher than those in the control group and this increase was statistically significant (P<0.05). Conclusion: According to the results, increased ACE activity can be an independent factor in the incidence of CAD and can be used to assess the risk of disease.