It has been known that Dexmedetomidine pre-medication enhances the effects of volatile anesthetics, reduces the need of sevoflurane, and facilitates smooth extubation in anesthetized children. This present study was designed to determine the effects of different doses of intravenous dexmedetomidine pre-medication on minimum alveolar concentration of sevoflurane for smooth tracheal extubation (MACEX) in anesthetized children. A total of seventy-five pediatric patients, aged 3-7 years, ASA physical status I and II, and undergoing tonsillectomy were randomized to receive intravenous saline (Group D0), dexmedetomidine 1 μg∙kg-1 (Group D1), or dexmedetomidine 2 μg∙kg-1 (Group D2) approximately 10 min before anesthesia start. Sevoflurane was used for anesthesia induction and anesthesia maintenance. At the end of surgery, the initial concentration of sevoflurane for smooth tracheal extubation was determined according to the modified Dixon's "up-and-down" method. The starting sevoflurane for the first patient was 1.5% in Group D0, 1.0% in Group D1, and 0.8% in Group D2, with subsequent 0.1% up or down in next patient based on whether smooth extubation had been achieved or not in current patient. The endotreacheal tube was removed after the predetermined concentration had been maintained constant for ten minutes. All responses ("smooth" or "not smooth") to tracheal extubation and respiratory complications were assessed. MACEX values of sevoflurane in Group D2 (0.51 ± 0.13%) was significantly lower than in Group D1 (0.83 ± 0.10%; P < 0.001), the latter being significantly lower than in Group D0 (1.40 ± 0.12%; P < 0.001). EC95 values of sevoflurane were 0.83%, 1.07%, and 1.73% in Group D2, Group D1, and Group D0, respectively. No patient in the current study had laryngospasm. Dexmedetomidine decreased the required MACEX values of sevoflurane to achieve smooth extubation in a dose-dependent manner. Intravenous dexmedetomidine 1 μg∙kg-1 and 2 μg∙kg-1 pre-medication decreased MACEX by 41% and 64%, respectively. Chinese Clinical Trial Registry (ChiCTR): ChiCTR-IOD-17011601 , date of registration: 09 Jun 2017, retrospectively registered.