Objective To define the optimal internal fixation method by means of studying the strength of various internal fixations of simulated fractures on posterior acetabular wall. Methods Eighteen preserved cadaveric hip joints were divided into three groups randomly. The simulated big isolated posterior wall fracture models were created by osteotomy in the middle of the outer rim of posterior acetabulum and the greater sciatic notch. The models were fixed with one of the three different methods: two cortical screws (CS), reconstruction plate (RP) and reconstruction plate plus two cortical screws (CS+RP). Then tests were performed on each model with 90°flexion of the hip. Measure the displacements of the fragments and the loadings when the displacements were 3mm. Results The displacements of fragments increased as the loading increased. There have high significant difference between the CS and RP or RP+CS (P<0.01), but no significance between the RP and CS+RP (P>0.05). Conclusion The ideal method of internal fixation of posterior acetabular wall fracture is RP. The strength of CS cannot maintain the stability of the fragment while RP+CS is not stronger than RP only and it may add more operative trauma and difficulty to operation.