Background: There are some conflicting results with Conventional Coronary Artery Bypass Grafts (CCABG) with arrested heart in coronary high-risk patients. Moreover, performing off-pump CABG in these cases may be associated with serious complications. The objective of this study is to evaluate the efficacy of the on-pump beating CABG (OPBCABG) in coronary high-risk patients in comparison with the conventional methods.Methods: In a prospective research study, 3000 off-pump CABG patients were considered during June 2003 to December 2011. Among these, 157 patients with one or more of the following risk factors were included for OPBCABG; severe left main stenosis, early post-acute myocardial infarction with ongoing chest pain, unstable angina, intractable ventricular arrhythmia, post complicated coronary intervention and severe left ventricular dysfunction. These patients were compared with 157 similar patients undergone CCABG with aortic cross clamp before 2003.Results: Preoperative patient characteristics revealed no significant differences between the two groups. The patients’ mean age and number of grafts were 57 years and 3 per patient respectively. Hospital mortality was 3.2% and 9% in OPBCABG and CCABG groups, respectively (P<0.001). Preoperative myocardial infarction, requirement of inotropic agents and intraaortic balloon pump, renal dysfunction and prolonged ventilation time were significantly higher in CCABG group.Conclusion: Our results suggest that OPBCABG is effective in coronary high-risk patients and significantly reduces mortality and the incidence of perioperative MI and other major complications.