Abstract: AIM To investigate the therapeutic effect of intra-aortic balloon counterpulsation (IABP) assisted off-pump coronary artery bypass grafting (OPCABG) in unprotected left main coronary artery (ULMCA) patients. METHODS We retrospectively investigated 28 ULMCA patients (15 males and 13 females) diagnosed by coronary angiography in our hospital from February 2008 to October 2013. The patients were divided into two groups according to the ULMCA conditions: IABP group ［n=15, nine males and six females, aged (62.5±7.7) years］ and non-IABP group ［n=13, 6 males and 7 females, aged (60.3±8.5) years］. Patients in both groups underwent off-pump coronary artery bypass grafting (OPCABG) and their invasive arterial systolic blood pressure (SABP), invasive mean arterial blood pressure (MABP), mechanical assisted ventilation time, ICU stay time, IABP assisted time, and the time of taking positive inotropic drugs were compared post-operation. Left ventricular ejection fraction (LVEF) was examined by ultrasonic cardiogram after 3 months. RESULTS Immediate operation success rate in both groups was 100%. Compared with those in non-IABP group, SABP and MABP in IABP group were significantly higher ［(92.5±3.7) mmHg vs.( 82.7±4.2) mmHg, P=0.000］; ［(77.6±5.3) mmHg vs.(60.5±6.0) mmHg, P=0.000］. Assisted mechanical ventilation time, ICU stay time, time using positive inotropic drugs in IABP group were shorter than those in non-IABP group. Patients in both groups were followed-up for 3 months. Ultrasonic cardiogram showed that LVEF in IABP group was higher than in non-IABP group after 3 months (48.5%±4.2% vs. 37.8%±3.8%, P=0.000). CONCLUSION For ULMCA patients undergoing OPCABG, proper use of IABP can reduce the risk and enhance the effect of the operation, promote recovery, improve cardiac function and reduce complications and perioperative mortality.