Human foot is capable of adapting to various diverse terrains，and this function is due，in part，to the foot’s capacity of varying its stiffness in different anatomical regions. In this study an adaptable robotic foot is developed by emulating the human foot’s arch，horizontal tie (the plantar aponeurosis，midfoot ligaments，etc.)，and its ability of varying its stiffness. A physiologically accurate 3D Finite Element (FE) model of foot and ankle is developed (with the details which are previously neglected in the literature)，and，is used to design an adaptable bioinspired robotic foot. The robotic foot is designed，analysed，optimized and fabricated as a semi-circular arch with a horizontal tie consisting of a Tunable Stiffness Mechanism (TSM). The active number of coils in parallel/series confi guration of concentric helical springs is changed to control the stiffness of the TSM. The arch stiffness and tunable stiffness range were optimized using multi ob jective genetic algorithms and epsilon constraint methods. Analytical and FE modelling results closely match the experimental validation of both the tunable axial stiffness behavior of the TSM and tunable bending stiffness of the robotic foot assembly. By implementing proper control algorithms，the proposed tunable stiffness robotic foot is capable of real-time adaptations to changing terrains，which may lead to the design and development of more adaptive walking robots.