Prosthetic knees are the devices for helping trans-femoral amputees to regain locomotion ability. When compared with passive prosthetic knees, quasi-passive and powered prosthetic knees with the ability to govern the motion of prostheses can significantly improve the stability and safety, at the same time enable exceptionally natural and effortless gait, even on difficult terrains. However, the mobile power source constrains the development and widespread use of these type of prostheses in terms of limited endurance and inconvenient daily charging. In this project, to handle the power source issue, we propose a self-powered smart prosthetic knee. In another project targeting the needs of below-knee amputee, experimental results indicated that our powered ankle-foot prosthesis when compared with widely used passive prostheses can reduce users’ metabolic cost by 15% and improve the symmetry of users’ gait, reducing the users’ effort required for walking.