The osseointegration trans-femoral implant is a new orthopedic anchoring method to attach prosthetic limb. The success of this technique depends on how healthy the osseointegration between implant and bone can be achieved and how the post-surgical rehabilitation is progressed. The current clinical practice is based on patient fitness feeling. To achieve a high success rate of osseointegration and an optimal rehabilitation process, a quantitative measurement of the degree of osseointegration is required. In this paper, the authors present a non-invasive method to determine the stability of an osseointegration trans-femoral implant system. It uses resonant frequency of implant system to observe the integration between the implant and bone. The vibration signals of a trans-femoral implant system were collected using an accelerometer attached to the implant abutment and analyzed using Fast Fourier Transform (FFT). The results of in vitro tests are presented to demonstrate that the developed instrument system can be used in future in vivo clinical research.