Objective：To determine the median effective concentration of remifentanil on targeted-controlled infusion（TCI） for smooth emergency from total intravenous aneasthesia and tracheal intubation in elderly patients. Methods：Twenty-four ASA Ⅰ-Ⅱ grade fe－male elderly patients undergoing elective jaw cyst surgery were enrolled in this study. Median effective concentration（EC50） was de－termined by Dixon’s up-and-down method. During skin suture，effect-site TCI of remifentanil was titrated to initial concentration of 1 ng/ml for the first patient. If the extubation was defined as smooth extubation，the predetermined concentration for the subsequent patient was decreased by 0.5 ng/ml. If it was considered failed smooth extubation，the predetermined concentration was increased by 0.5 ng/ml for the next patient time. The EC50 of remifentanil was calculated by the Dixon’s up-and-down method and the EC50 and 95％ confidence interval（CI） were analyzed using the probit teat in a logistic regression model. Mean arterial pressure（MAP） and heart rate（HR） were compared in patients with smooth extubation and without smooth extubation. Results：The EC50 of remifentanil for smooth emergency from aneasthesia and tracheal intubation in elderly patients was 0.94 ng/ml by the Dixon’s up-and-down method，the EC50 and 95%CI of remifentanil was 0.99 ng/ml（95%CI 0.52 ng/ml-1.51 ng/ml）by probit analysis respectively． MAP and HR were lower in patients with smooth extubation than in those with failed smooth extubation during tracheal extubation（P<0.05）. Conclusion：Maintaining a remifentanil infusion at the optimal concentration of 0.94 ng/ml can suppress coughing associated with tra－cheal extubation and haemodynamic changes，almost without significantly delaying recovery from anaesthesia and thereby targeting smooth extubation for 50% of the elderly patients.