Abstract: 　Objective　In this study，provides a reference for the selection of modified miniplate implants in different clinical directions for maxillary protraction. Methods　The three-dimensional CAD model of six forms of modified miniplate implants was constructed and assembled with maxillary model to obtain the final model.A force of 4.9N on each side was apply to that traction sites of the model,and the direction was 0°to 50°with the maxillary occlusal plane.Results The stress of that modified miniplate implants and the tension and stress of the implants are analyzed under each working condition.The force of retention screw is different, and it shows different trend with the change of angle. When the angle is 0°, Y3 miniplate implants retention screw is less 3.899, and when the angle is 10°-40°，L3 miniplate implants retention screw is less 4.544、4.170、3.820、3.547 and when the angle is 50°，L2 miniplate implants retention screw is less 2.687.Conclusion In order to achieve more stable curative effect, the modified miniplate implants should be used to assist the maxillary hypoplasia patients to draw in different directions. When the angle between the traction direction and occlusal plane is 0, Y3 miniplate implants should be used; When the angle between the traction direction and the occlusal plane is 10-40 degrees, L3 miniplate implants is selected; L2 miniplate is selected when the angle between traction direction and occlusal plane is 50 degree.

Key words: maxillary hypoplasia, maxillary protraction, zygomatic alveolar ridge, bone anchorage