Objective: Study of the biomechanical effect on power arm for en-masse retraction of anterior teeth using clear aligner and mini-screw, providing reference for clinical application. Method: Building the 3-D mode of power arm, which is 6mm high, was attached to the canine or appliance. To analysis the initial displacement and the maximal periodontal ligament vonmises stress of the teeth in three loading conditions, the force was loaded by ①clear aligner+150g force of retraction at canine②clear aligner+150g force of retraction at power arm at appliance③clear aligner+150g force of retraction at power arm at canine. Result：In sagittal direction, the crown and root displacement difference of maxillary central incisor is 1.29E-01mm, 1.29E-01mm, 1.33E-01mm,respectively. The crown displacement of the maxillary first molar is -2.33E-02mm, -2.35E-02mm, -2.68E-02mm, respectively. The maximal periodontal ligament vonmises stress of the central incisor is 4.84E-02 MPa,7.26E-02 MPa,4.00E-02Mpa respectively and the first molar′s is 5.33E-03Mpa,1.05E-02Mpa,5.78E-03Mpa respectively. Conclusion: It can not be testified that retracting on the 6mm high Power arm at canine or appliance with 5mm high mini-screw has more advantage than on the canine directly for controlling the torque of incisors , saving anchorage of posterior teeth and decreasing the periodontal ligament vonmises stress.