Objective To develop a new hemi-arthroplasty system-Trochanteric Prosthesis System (TC) for the treatment of unstable femoral intertrochanteric fractures in the elderly, so as to preserve bone mass and meet requirement of functional exercises at early stage. Methods A normal male adult volunteer was chosen to receive CT scanning at middle and upper regions of his both intact femur. The serial digitized image data of spiral CT in DICOM format were imported to finite element modeling software to establish a three-dimensional (3D) solid model of the proximal femur. The Pro/E software was used to conduct computer-aided design of the new hemi-arthroplasty prosthesis system and then its metal model was also made by rapid prototyping techniques. After repeated verification and improvement on cadaver femur, the femoral prosthesis was molded and assembled in the solid fracture mode for finite element analysis. The unstable femoral intertrochanteric fracture model obtained from the fresh cadaver of an elderly male was chosen to make A2.2 Type of such fracture model in AO classification system. The new hemi arthroplasty prosthesis system was implanted and assembled into the model and received mechanical testing, including material performance testing, prosthesis head/neck and stem fatigue testing, anti-compression and anti-torsion testing, according to the National Industrial Standard YY0117 and YY0118. Results The sample of new hemi-arthroplasty prosthesis sustained 5 million cycle (8 Hz) fatigue testing on the part of the head-neck and the stem body without any breakage and failure. With the sample implanted into the intertrochanteric fracture model, the maximum compressive strength and torsional strength of the sample reached over 2 kN and 15.5 N?m without failure, respectively. The contact stresses between the stem and the femur were mostly distributed at the region below the femoral trochanter, where the maximum average Von Mises stress values were 17.6~26.4 MPa. Stresses at the region of intertrochanteric fractures were at a low level. The maximum average Von Mises stress values at the greater and lesser trochanter region were 2.7 and 4.9 MPa, respectively. Conclusions The new developed hemi-arthroplasty prosthesis has the advantages of easy performance, reliable fixation, sufficient bone preservation and it is capable of fulfilling the demands of early weight bearing and functional exercises. It is suitable for the treatment of unstable femoral intertrochanteric fractures in the elderly.