The present study was to examine the effect of stellate ganglion block (SGB) on bilateral regional cerebral oxygen saturation (rSO2) and postoperative cognitive function. Eighty patients undergoing selective coronary artery bypass graft with cardiopulmonary bypass (CPB) were randomly and equally divided into two groups. The patients in group S were given right SGB with ropivacaine, while the patients in group C were injected with normal saline. We compared the bilateral rSO2 after SGB. Minimum Mental State Examination (MMSE), Visual Verbal Learning Test (VVLT), and Digital Span Test (DST) were applied to observe the effect on cognitive function. We found that the incidence of postoperative cognitive dysfunction (POCD) 7 days after surgery in group S was lower than that in group C. The level of blocked side rSO2 of S group were significantly higher before CPB time of rewarming than that before SGB (P＜0.05), much higher than corresponding non-blocked side rSO2 before CPB (P＜0.05), and much higher than rSO2 level in group C before CPB and after CPB(P＜0.05). The non-blocked side rSO2 in group S before anesthesia were much lower than basic levels and those in group C (P＜0.05). It could be concluded from the above results that there was significant increase in the blocked-side rSO2 compared to the non-blocked side and there was significant decrease in the incidence of POCD compared to the control group after SGB.