A new design method and a simple manufacturing tool are developed for a novel parametric curved-segment prosthetic foot based on compliant mechanisms. While current elastic energy storage and return feet have been widely commercialized, those designs still haven't fully taken advantage of compliant mechanisms. The design in this research would help to reduce the fabrication and assembly cost but still preserves the flexibility which is the key characteristic to improve amputee gait. A shape and size optimization scheme via genetic algorithm and finite element method is undertaken to design the device. Prototypes of the devices are fabricated and tested. The stiffness of the prosthetic foot predicted by theory is verified by experiments. Using the proposed design methodology model stiffness and levels of strain energy stored inside the flexible segments could be easily regulated.