【Abstract】 Objective To investigate The effect of preconditioning with Soflurane inhalation on postoperative cognitive function in patients undergoing off-pump coronary artery bypass grafting. Methods Sixty patients undergoing elective OPCABG, aged 55~75,ASAⅡ or Ⅲ, were randomly divided into two groups: Soflurane preconditioning group(S, n = 30) and propofol group(p, n = 30). The blood samples of internal jugular vein were taken for determination of serum S100β protein, nerve basic peculiarity alkene alcoholization enzyme (NSE) and superoxide dismutase (SOD) after anesthesia induction(T0), The end of operation (T1), 6 h after operation (T2) and 12h after operation (T3) , 24h after operation (T4). A mini-mental state examination (MMSE) was performed 1d before and 3 and 7d , 3m after operation by an experienced anesthesiologist. Results All patients Complete MMSE. The incidence of POCD was higher within 3m after operation in group P (43.3%) than that in group S (16.7%, P<0.05). The scores of MMSE were lower at 3 and 7 d after operation than that at 1 d before operation in both groups( P<0.05).Compared with preoperative 1d, S group 3m postoperative scores was no statistically significant difference. However, in P group the difference was statistically significant. Group P MMSE scores were lower than S group 3d postoperative(P < 0.05), two groups of 7d and 3m MMSE scores were not significant difference. The contents of serum S100β protein and NSE increased at the initial stages of operation, and reached the peak at T1 (P<0.05); then decreased at T2、T3 (P<0.05), and returned to the baseline level at T4 in both groups (P>0.05). Compared with the group S , the content of serum S100β protein was remarkable increased in group P at T1 and T2(P<0.05) ,The content of serum NSE was significance difference in group P at T2(P<0.05). At T3 and T4 , The content of serum SOD was significance increased in group S(P<0.05). Conclusion Soflurane preconditioning can decrease incidence of POCD in patients undergoing OPCABG.