During open cardiac surgery that the heart should be suspended, for preventing damage of other tissues and organs, vasopressors drugs have been used for maintenance of blood pressure. The aim of this study was the comparison of infusion and bolus injections of phenylephrine on hemodynamic stability during cardiopulmonary bypass and their effects on bicarbonate and lactate blood level. In this randomized double-blind clinical trail, 88 patients who were candidate for onpump coronary artery bypass grafting, were considered and then divided into the infusion and bolus groups. In the beginning and at the end of study, the blood pressure and laboratorial variables was recorded and finally analyzed by SPSS software. According to the obtained information, out of 88 examined patients, 52.2% of them were received phenylephrine in bolus regimen while 47.8% were received phenylephrine in infusion regimen. The mean age of patients in the bolus and infusion groups was 56.59 ± 19.5 and 59.2 ± 10.16 years, respectively. The results show that there were not statistically significant differences in mean values of the MAP, PH, HCO3 and lactate between two groups. The results show that the infusion injection of phenylephrine has no advantage than bolus injection on hemodynamic stability during cardiac pulmonary bypass, and on the bicarbonate and lactate blood level.