Objective The purpose of this studywas to investigate the effects of Fr¨ankelⅡappliance on the upper airway of children.Methods The subjects consisted of 20 patients with Angle ClassⅡ, division I malocclusion (10 males and 10 fe- males). The ages of all caseswere ranged in 9~10 years. Each experimental subjectwas also served as self-control and cephalo- metric analysis was conducted.Results Compared with the results of pretreatment, the distance of PNS-Ba, SPP-SPPW, P-T, V-LPW and theMcnamara line increased remarkably.Conclusion The Fr¨ankelⅡappliance can improve the sagittal dimensions of the upper airway in children.