Objective：To establish a simplified three-dimensional finite element model of orthodontic anchorage micro-implant,and to study the biomechanical changes of the micro-implant-bone interface when embedded in different directions,so as to provide a theoretical basis for clinical application of the micro-implant.Methods:I-DEAS finite element analysis software was used to establish a micro-implant and bone finite element model.The micro-implant was embedded into the bone at an angle of 30°.The orientation of the loading force and the embedding angle were kept unchanged; using the embedded point as the center of a circle and the projective line of micro-implant on the bone surface as the radius,5 different embedding directions,including 0°,45°,90°,135° and180°,were chosen.A simulated orthodontic force of 200 g was loaded parallel to the surface of bone in the embedded region,and the stress distribution and displacement changes on the micro-implant-bone interface were analyzed.Results:The changes of stresses and displacement were within the clinicophysiological range in all groups.The embedded region of micro-implant and the cortical bone were stress-focused areas.The changes of Von-mises stress,stretching stress and compressive stress were largely the same; the stress distribution had a decreasing tendency.Under retentive force,the stresses of group 0° and 45° were smaller than those of the other groups,with group 0° having the smallest one.The displacement of group 0° and 45° were evidently larger than those of group 90°,135° and 180°,with that of group 90° having the smallest one.Conclusion:The micro-implant embedded with different directions can safely bear 200 g force parallel to the surface of bone in embedded region.When choose the embedding directions of micro-implant,efforts should be made to reduce the retentive effect of the loaded force to keep the stability of micro-implant.