Purpose To explore the variation of contact characteristics of acetabular posterior wall fracture and its internal fixation.Methods Contact areas and contact stress of normal acetabulum group、acetabular posterior wall fracture group and two methods of internal fixation groups(reconstruction plate alone and spike plate with reconstruction plate) were measured by the application of pressure film,respectively.Results Compared with normal acetabulum group, contact area of acetabular posterior wall fracture group decreased by 34%,and recovered by 82% with reconstruction plate alone,and which spike plate group regained 92% contact area.Acetabular contact pressure and contact stress both increased obviously in acetabular posterior wall fracture group,and showed decrease after the fractures were fixed by the two internal fixation methods.Conclusions Contact areas of acetabular posterior wall fracture group greatly decreased to cause stress concentration.Two methods of internal fixation effectively made the acetabular contact areas recovered and reduced contact stress.Spike plate group were more effective compared to reconstruction plate alone group.