Abstract: Objective To explore the role of nalmefene in prevention of fentanyl-induced bucking in patients with induction of general anesthesia and observe its influence on hemodynamic during intubation.Methods 80 patients with ASA ⅠtoⅡ were randomly divided into nalmefene group (group Ⅰ)and the control group (group Ⅱ).All patients were injected with phenobarbital sodium 30 mg and atropine 0.5 mg 30 minutes before induction of anesthesia.0.25 μg /kg of hy-drochloric acid natrium nalmene and the same capacity of physiological saline was applied 2 minutes before induction of intravenous for group Ⅱ and Ⅰ respectively.Coughing cases (incidence)and the intensity,blood pressure,heart rate ,pulse oxygen saturation before anesthesia induction,60 second after fentanyl injection and after intubation were observe between two groups.Results In-cidence rate of cough was 0% in group Ⅰ,which was significantly lower than 60% in group Ⅱ(P < 0 .0 5 ).Strength of coughing in group Ⅱ was much more intensive than that in group Ⅰ(P <0.05).The hemodynamic parameters after fentanyl injection in group Ⅰ was more steady than that in group Ⅱ (P <0.05),and there was no significant difference of hemodynamic response to intubation between two groups (P >0.05).Conclusion Preventive injection of nalmefene can effectively prevent coughing response to fentanyl injection during induction of anesthesia and im-prove the hemodynamic instability.