The tibial shaft fracture model was customized by reverse engineering and 3D printing technology, and the biomechanics of the Orthofix Unilateral External Fixator for tibial shaft fracture was studied. Through the design of an orthogonal experiment scheme, the distribution of the Schanz’s nails on the clamp, the distance from the lateral the Schanz’s nails to the fracture end, and the distance from the tibia to the external fixture were measured by the XTDIC-CONST 3D Full-Field Strain Measurement and Analysis System. The experimental results show that when the number of the Schanz’s nails decreased, the bending deformation of the Schanz’s nails will increase from pressure load, which increases the possibility of plastic deformation and fatigue fracture of the external fixator. According to the mechanical analysis results of the nine schemes, the distance from the external fixture to the tibia has the most significant effect on the deformation of the Schanz nail. When installing six Schanz pins in the clip, the distance from the lateral Schanz’s nail to the fracture end is 120 mm, and the distance from the external fixture to the tibia is 30 mm. The comprehensive performance of the scheme is the best.