Ｏｂｊｅｃｔｉｖｅ　To observe the effect of low dose dexmedetomidine on emergence agitation after tonsillectomy and/or adenoidectomy in children with sevoflurane anesthesia.　Methods　Ninety children， aged 2 y-8 y， ASAⅠ-Ⅱ， undergoing adenotonsillectomy and/or Adenoidectomy， were randomly divided into two groups： the dexmedetomidine group（D group， n=45） and the saline group（S group， n=45）. Anesthesia was maintained with sevoflurane and oxygen. D group patients were given dexmedetomidine 0.3 μg/kg （in 10 min） and maintained with 0.2 μg·kg-1·h-1. The S group was given the same dosage saline. Intraoperative hemodynamics were recorded every 5 min. Time of spontaneous breathing， time of extubation， and the emergence agitation in PACU were recorded.　Results　The incidence of emergence agitation was 28.89% in group D， and 64.44 % in group S, the mean agitation scores in the D group were lower than the S group except at 10 min.　Conclusions　So low dose dexmedetomidine could reduce the emergence agitation in children receiving sevoflurane undergoing tonsillectomy and/or adenoidectomy.