Objective:To study the method and complications exactractions of the mandibular third molars in orthodontic patients.Methods: To extract 32 teeth in 16 cases in orthodontic teenager patients by elevating flap and removing the bone covering of the third molar,cut the tooth into four parts by high speed turbine engine,study the postoperative complication.Results: The mandbular third molar locate distal and buccal surface to the second molar.All the teeth extract smoothly in 23± 2min,the postoperative course was uneventful.There were no numb of the lower lib and damage of the second lower molar.Conclusion: Remove the bone covering of the mandibular third molars and cut the tooth into four parts with air turbine handpiece is useful.