Objective：To observe the effects of 0.4 μg/(kg·h) dose of dexmedetomidine on intra-operative wake-up test in children patients undergoing scoliosis surgery． Methods: Sixty patients for posterior scoliosis correction (ASA Ⅰ-Ⅱ， aged 5-16 years) from March 2013 to April 2015 were enrolled in this prospective, double-blinded, randomized, placebo-controlled study, The patients were randomly classified into two groups to receive dexmedetomidine (group RD, n=30) or saline solution (group R, n=30). In group RD, dexmedetomidine ［0.4 μg/(kg·h)］ was administered after tracheal intubation, while the equal volume saline solution was given instead in group R. Anesthesia was induced with midazolam, propofol, sufentanyl and cisatracurium, and anesthesia was maintained with sevoflurane inhalation and a continuous intravenous infusion of remifentanil in the both groups.BIS（bispectral index，BIS） value was maintained at 40－60,and mean arterial pressure (MAP) was maintained at ≥ 60 mmHg before the wake-up test.When the wake-up test was performed, immediately the dexmedetomidine and remifentanil infusion were stopped, and the end-tidal concentration of sevoflurane was adjusted to 0. Mean arterial pressure, and heart rate (HR) were recorded before anesthesia and at 5-minute intervals during the wake-up test. The wake-up test time, arousal quality and sedation scores were recorded also.In addition, the data were also gathered on the dosage of ephedrine and atropine were used, as well as the intraoperative awareness in the patients who were followed up on the first day after the operation．  Results: There were no differences between group RD and group R with regard to HR and MAP at getting into the operation room （t=-1.460，P=0.150;t =-1.015, P=0.315 ）. In group RD, no evidence was found for a difference in HR and MAP at awakening up versus at getting into the operation room （t=0.974,P=0.340；t=-1.449,P=0.161）, while in group R, an increase in HR and MAP occurred at awakening versus at getting into the operation room （t=-2.106，P=0.044；t=-2.352，P=0.026）.There were no significant differences in sedation scores and wake-up test time between the two groups（t=1.986，P=0.052；t=0.392，P=0.697）. The wake-up test quality was significantly better in group RD than in group R （t=-2.098，P=0.041）．HR in group RD was significantly lower than that in group R at any time point during the wakeup test (P<0．05)． Four patients had awareness occurrence during the operation in group R,and no awareness occurrence in group RD. Conclusion: Dexmedetomidine， when administered at a rate of 0.4 μg/(kg·h) as an adjuvant of sevoflurane inhalational anesthesia, could improve the wake-up test quality， and maintain hemodynamic stability during scoliosis surgery．