Objective:To evaluate the clinical effects of invisible bracketless appliance on the upper molar distalization.Methods:15 patients with class Ⅱ malocclusion(at the average age of 25.3 years) were treated by invisible bracketless appliance,the pre and post three-dimensional digital models were superimposed and measured,the effects of molar distalization were analysed.Results:After treatment,the maxillary first molars were distalized by 2.58 mm on both sides.The left and fight second molars were distalized by 2.57 mm and 2.68 mm respectively.Bilateral central incisors were moved mesially by 0.34 mm.There was no significant difference in the horizontal movement of central incisor.But the left and fight first molars were moved buccally by 0.96 mm and 0.97 mm respectively,the left and fight second molars were moved buccally by 1.01 mm and 1.11 mm separately.Bilateral first molars were intruded by 0.26 mm,the left and right second molars were intruded by 0.37 mm and 0.36 mm,respectively.But the central incisors had no significant vertical movement.There was no significant difference in the buccally or palatally rotation of bilateral first and second molars.Conclusion:Invisible bracketless appliance is efficient for distalization of upper molar,but it may result in mild molar intrusion and anterior anchorage loss.