Ｏｂｊｅｃｔｉｖｅ　To investigate the effects of dexmedetomidine on adverse events during recovery period in children with obstructive sleep apnea syndrome operation.　Methods　One hundred and twenty ASA physical status Ⅰ-Ⅱ children， aged 2 y-6 y， undergoing general anesthesia for tonsillectomy and adenoidectomy， were randomly divided into 3 groups （n=40）： group D， group M and group P. Heart rate（HR）， mean arterial pressure（MAP）， pulse oxygen saturation（SpO2）， partial pressure of end-tidal carbon dioxide（PETCO2） and bispectral index（BIS） were monitored in all patients when arriving in the operation room， and a intravenous catheter was inserted into the peripheral vein. The children were administered with midazolam， propofol， remifentanil and rocuronium for induction， while remifentanil and propofol ｔarget-ｃontrolled ｉnfusion for maintenance. Twenty min before the end of the surgery， in group D dexmedetomidine 0.4 μg/kg and in group M midazolam 0.05 mg/kg and in group P 0.9% NaCl were infused intravenously within 10 min. HR and MAP were recorded before anesthesia（T0）， before intravenous administration（T1） ， 1 min（T2） and 5 min（T3） after administration， 1 min before extubation（T4）， the moment（T5）， 3 （T6）， 5 （T7）， 10 （T８）， 20 min（T9） after extubation. Time to extubation and emergence， the incidence of adverse events during recovery period were recorded.　Results Time to emergence in group M［（14±4） min］ were significantly longer than in group D ［（11±4） min］ and group P［（12±4） min］（P＜0.05） while the modified Aldrete score after entrance into PACU（6） were significantly lower （P＜0.05）. HR［（95±16）， （96±16）， （101±17）， （103±17）， （101±16）， （100±16）， （101±17） bpm］ and MAP［（73±10）， （71±9）， （78±10）， （79±11）， （77±10）， （77±10）， （75±10） mmHg（1 mmHg=0.133 kPa）］ were significantly lower at T2-T8 in group D compared with group M and group P（P＜0.05）， and the incidence of laryngospasm（5%）， oxygen desaturation<92%（5%） and laryngospasm score（0）， cough score（1） were also significantly lower in group D （P＜0.05）. The incidence of breath holding in group D（12.5%） was significantly lower than in group P （P＜0.05）. The pediatric anesthesia emergence delirium（PAED） scale at 10 min（8 and 9）， 20 min（9 and 10） and 30 min（8 and 9） after entrance into post-anesthesia care unit（PACU） were significantly lower in group D and group M compared with group P（P＜0.05）.　Conclusions　Without interfering in recovery time，dexmedetomidine infused 20 min before the end of surgery effectively reduces adverse events during recovery period in children with obstructive sleep apnea syndrome.