Abstract: Traditionally,the clinical femur fracture reduction surgery is imperfect and often results in misalignment and high intraoperative radiation exposures.To solve the problem,a method for fracture reduction based on preoperative CT image and 6 degrees of freedom parallel mechanism which is fixed to unhealthy femur is proposed.Based on the body's symmetry principle,the method uses contralateral femur as a standard to guide the reduction of femoral shaft fractures.By twelve markers on the implementing machine/the computer can calculate the length of pole in the virtual space in real time. Finally,animal bones experiments show the effectiveness of the approach.