Objective To establish a finite element model of mandibular distraction and to evaluate its biomechanics and deformation. Methods The geometry model was established by Mimics software via reading the data of DICOM format from CT. Bone cutting simulation was performed by Mimics and model optimization was operated by Magics software. The finite element model was established and mandibular distraction simulation was analyzed by Ansys software. Results The dis-placement of mandible, the stress and the soft tissue change were all calculated. Conclusion The finite element analysis can evaluate the operative effect, analyze the stress distribution and the direction of soft tissue resistance, which could guide the preoperative design and improve the clinical outcome.