Objective　To investigate the effects of acetabular prosthesis position on the reconstructed hip funcion after the total hip arthroplasty by 3D finite element analysis.　Methods　Using a special designed biomechanical semi-automatic mesh generator, a high quality specific 3D finite element model of the hip bone was generated from the CT scan data of a patient with hip joint dysplasia. And then the acetabular prosthesis was integrated at the true acetabular position, compared with penetration position, and the position above the true acetabular, to investigate the position infuence of acetabular prosthesis for the total hip arthroplasty. Finally, all models were simulated under same loading conditions.　Results　(1) The model with acetabular prosthesis placed at the true acetabular position provided the optimal silumation result, with smallest principal stresses and sheer stresses; (2) The model with penetration position resulted some bigger stresses than the true acetabular position; (3) The model with position above the true acetabular resulted much bigger stresses. Conclusions　The acetabular prosthesis for the total hip arthroplasty should be placed at the true acetabular position as possible, to provide the optimal stresses distribution and functinal repair.