Objective Based on computer three?dimensional finite element technology， this study investigates the biomechanical properties of different internal fixation materials for Haraguchi typeⅡ ankle fractures， determines the optimal internal fixation material for ankle fractures， and provides basic theoretical support for clinical practice. Methods Using computer three?dimensional finite element technology， a three?dimensional finite element model was established for the fixation of Haraguchi typeⅡ posterior ankle fractures using three different internal fixation materials： posterior ankle hollow screw fixation and inner ankle hollow screw （Group A）， posterior ankle support steel plate fixation and inner ankle hollow screw （Group B）， and posterior ankle reconstruction steel plate fixation and inner ankle hollow screw （Group C）. Biomechanical analysis was performed on the model to compare the advantages and disadvantages of the internal fixation materials in each group. Results The maximum principal stress and tibial stress of the two steel plate fixation models were significantly lower than those of the three hollow screw fixation model group， while the stress of the reconstructed steel plate group was lower than that of the supporting steel plate group； Among the three models， the stress reconstruction of the hollow screw at the inner ankle was the smallest in the steel plate group and the largest in the hollow screw group； The total displacement range of the tibia is the largest in the hollow screw group， followed by the supporting steel plate group， and the smallest in the reconstruction steel plate group. Conclusion Reconstructing steel plates to fix Haraguchi typeⅡ ankle fractures has the strongest biomechanical stability and is a relatively ideal fixation method， which has certain guidance for clinical practice.