Objective To investigate a reasonable and effective internal fixation method for posterolateral fracture of the tibial plateau. Methods Specimens of the tibial plateau with posterolateral fracture made from 12 adult male cadavers were randomly and evenly divided into 3 groups, and fixed by anterior 6.5 mm lag screw, lateral 4.5 mm L-shape plate, posterior 3.5 mm T-shape plate, respectively. All the specimens were loaded in turn by stress of 250, 500, 750, 1 000 N, and the corresponding axial displacement and stress were measured. Results Under the same stress, the Y-axial displacement of the anterior lag screw group was the smallest, showing a significant difference with the lateral plate group and the posterior plate group, while there was no significant difference between the lateral plate group and the posterior plate group in the Y-axial displacement. The stresses on marked points in the anterior lag screw group were evenly distributed. Conclusions For fixation of isolated posterolateral fractures of the tibial plateau, the anterior 6.5 mm lag screw can effectively increase the axial stability and balance the stress distribution around the fracture block, indicating it is an effective method for mechanical fixation. The lateral plate has certain advantage in lateral stability control, while the posterior plate has certain value to reduction of the posterior tibia plateau fracture.