Aiming at the filature of titanium plates and screws after defective mandible reconstruction surgery, a method named Finite Element Analysis （FEA）was conducted in this paper through FEA software Abaqus with which a 3D model of defective mandible was established. The mandible 3D model was input into the Magics and remeshed. The mandible model was output in the format of .inp file from the Magics and import to Abaqus for converting from triangular meshes to tetrahedral meshes. The tetrahedral meshes totally had 71057 tetrahedral elements and 10720 nodes. The boundary constraints of the mandible 3D model were arranged. The force was applied separately in the direction of vertical, 15° and 30° with the occluding plane (teeth force range when occluding) to analyze the force. The mandible 3D model was established and prepared to be done a biomechanical analysis.