Abstract: Objective　 Establish craniofacial model to analysis effects of different anterior traction directions and traction sites on the craniofacial complex during protraction combined with expansion. Methods　 Three-dimensional finite element model with 3 types (L1, L2, L3) maxillary palate skeletal protraction assisted expansion using reverse engineering method. When the palate is extended, a force of 500g is applied to the traction hook of the device, and the directions are 0 °, 15 °, 30 °, and 45 ° with the maxillary occlusal plane. The stress distribution and displacement trend of the craniofacial complex are analyzed. Results　 At the same traction angle, there is no statistical difference in the three-dimensional displacements of the three points of the N points (Nasion), IOB point (Infraorbital point), and A point (Subspinale) in L1, L2, and L3；L1, L2, and L3 groups have different stress values from the same bone suture；With the increase of the traction angle, the displacement values of the N, IOB, and A points in the Z direction decrease linearly；The same traction force produces different stresses in each bone suture, and the stress changes of each bone suture with the increase of the traction angle. Conclusions　 When maxillary palate skeletal protraction combined with expansion，the three device forms have little effect on the displacement trend of the craniofacial, which can cause the craniofacial to move forward with counterclockwise rotation, but L2 Relatively low stress on the same bone gap, with the increase of the traction angle, the counterclockwise rotation of the craniofacial decreases, and the stress of each bone suture changes differently. In the clinical application of the zygomatic bone support device for forward traction, a smaller traction angle can be selected for patients with deeper occlusion and deeper coverage, on the contrary, for patients with shallow occlusion and shallower coverage Large traction angle.

Key words: Skeletal expansion, Maxillary protraction, Three-dimensional finite element