Ｏｂｊｅｃｔｉｖｅ　To investigate the concentration of remifentanil for inhibiting 50% patients from circulatory response (EC50) during extubation under total intravenous anesthesia, in order to guide clinical anesthesia.　Methods　A total of 30 ASA Ⅰ or Ⅱ patients without cardiac surgery under general anesthesia from June to August 2016 in our hospital were included. Anesthesia were induced by remifentanil combined with propofol under BIS monitoring. Propofol was discontinued at the end of operation, and remifentanil doses were adjusted to test concentrations. According to the up-and-down method, the concentration of remifentanil was set as follows: the target plasma concentration of remifentanil was 2 μg/L for the first patients, with an interval concentration of 0.2 μg/L. Then, the MAP and HR were recorded before anesthesia induction(T1), when remifentanil dose reached test concentrations before extubation(T2), immediately after extubation(T3), 1 min(T4), 2 min(T5), 3 min(T6), 4 min(T7), and 5 min(T8) after extubation.　Results　All the operations were completed successfully and all patients received a single dose of muscle relaxants. The operation time was less than 2 h. There were no severe stress response, bradycardia and hypotension and other adverse events during operation. No skin itching, pain, nausea and vomiting and other complications were reported after extubation. There were 6 patients who coughed after extubation. According to the up-and-down method, EC50 of remifentanil for inhibiting circulatory response was 1.637 μg/L (95%CI=1.481-1.769 μg/L).　Conclusions　When remifentanil and propofol are used in combination for total intravenous anesthesia, the concentration of remifentanil for inhibiting 50% patients from circulatory response during extubation was 1.637 μg/L.