Stress concentration is one of the main mechanical problems leading to the failure of clinical application for osteointegrated implant of percutaneous osteointegrated prosthesis, which is especially marked for higher amputated leg prosthesis. Traditionally design was composed of only the distal part. To improve the biomechanical safety, a new design with the lag part similar to the lag screw was introduced. Based on CT scan data, relatively accurate model of femur for finite element analysis (FEA) were obtained. The FEA results with the new implant demonstrated that compared to traditional design, the declination of bone stress peak ranged from 15.68% to 28.67%, perpendicular deformation from 34.73% to 72.16%, and maximal stress of implant from 14.51% to 23.36% with the increasing of loads from 3750N to 2000N. So the new design of osteointegrated implant would be more secure mechanically, in the case of higher amputated leg attachment.