Objective：To evaluate efficacy and postoperative morbidity in tonsillectomy using the harmonic scalpel vs conventional electrocautery. Materials and Methods：1) We compared intra-operative bleeding and operation time and analyzed the degree of pain, oral feeding and the ability to return to normal activities from the questionnaire. 2) Animal study：Using rats, we made each linear wound with harmonic scalpel or electrocautery, then compare the width of thermal injury area with trichrome stain. Result：Harmonic scalpel tonsillectomy had significant advantages over electrocautery tonsillectomy in terms of post operative pain, oral diet tolerance and the time of return to normal life. In addition, it increased patients’ overall satisfaction with the surgery. In animal study, it was found that the thermal injury was less severe in the wound caused by harmonic scalpel than by electrocautery. Conclusion：Harmonic scalpel tonsillectomy decreases the thermal injury of the adjacent tissue, thus it has advantages over electrocautery in post tonsillectomy morbidity.