Objective:To evalate the effect of remifentanil(0.3 μg/kg) bolus on the efficacy of propofol during target-controlled infusion(TCI) of propofol anesthetized analgestic artificial. Methods:Forty-two young patients undergoing painless artificial abortion were randomly allocated to two groups:propofol group(group P,n = 20) and propofol plus remifentanil group(group RP,n = 22). Patients were sequentially given different doses propofol so that the 50% target propofol plasma concentration(Cp50 which there is a 50% chance that patients show no movement in response for dilatation or curettage of cervix and uterine aspiration) could be determined by up-and-down sequential test. Anesthetic depth was observed by S/5TM Entropy. Heart rate(HR),mean arterial pressure(MAP),pulse oxygen saturation(SpO2),state entropy(SE) and response entropy(RE) were continuously monitored during anesthesia. Modified Observer’s Assessment of Alertness/Sedation scale(MOAA/S) was used to detect the level of consciousness. Comparison of MOAA/S with RE and SE was performed with the Spearman correlation coefficient. Results:Propofol consumption and target propofol plasma concentration(Cp)were less than those in group P(P < 0.01). Cp50 of cervix dilatation was 3.495 vs. 4.637μg/kg in the group RP and group P. Cp50 of cervix dilatation was 4.417 vs. 5.825 μg/kg in the group RP and group P. RE and SE of group RP were significantly higher than those of group P(P < 0.01 or P < 0.05) during operation but there were similar in the both groups during awaken time. MOAA/S was well positively correlated to RE and SE(P < 0.01) in both groups. Conclusion:In young female patients,0.3 μg/kg remifentanil bolus can effectively decrease Cp50 values for TCI propofol and depth of anesthetic sedation,but it can not influence the ability of Cp and spectral entropy to predict and detect MOAA/S during painless artificial abortion.