Abstract: Objective: To explore the construction of mechanical model of straight wire appliance for mandibular arch by three-dimensional finite element modeling. Methods Scanning of images of individual madible and dentition with normal occlusion was made through muti-slice spiral CT scanner. Data were imported into mimics software in the format of DICOM. Difference in gray values was used to reconstruct mandibular jaw and dentition. Cloud data of jaw and dentition points were imported into geomagic studio 8.0 in the format of txt to construct triangular meshes. Carry out NURBS surface fitting to generate entity model of jaw and dentition. Data were imported into ansys software in the format of igs. Build the model of straight-wire bracket and arch wire in ansys. In geomagic studio 8.0, augment root surfaces by 0.25 mm to generate the periodontal membrane, and carry out Boolean operation to generate assembly model of teeth, jaws, periodontium, brackets and wires. Result A three-dimentional finite element model of straight wire appliance was constructed. In ansys, partition the model, divide the meshes, and impose certain constraints and loads, then mechanical analysis of three-dimensional finite element could be carried out. Conclusion Building three-dimensional finite element model of straight wire appliance by spiral CT imaging and by combing merits of mimics, geomagic studio and ansys is precise, effective, simple, practical, operable and less time consuming.