This paper aims to develop a multi-legged stair climbing robot with the capability to steadily climb stairs with consistent human foot trajectory. The leg design is based on the eight-bar Jansen mechanism but a new set of leg configuration is numerically identified based on the optimal design method with the aim to mimic the human foot trajectory when climbing stairs. The kinematic analysis of the leg mechanism based on loop closure equation has been derived in order to identify the leg trajectories for various designs. The targeted foot trajectory is experimentally measured. The weighted sum and simplex methods are used to solve the multi-objective function in the optimal design process. The proposed design is an eight-leg robot; its dynamic performance and trajectories of the multibody motion when climbing stairs have been numerically verified by using the commercial CAE package, RecurDyn. The prototype of the biomimetic robot has been developed to proof the concept design. The experimental results show the multi-legged robot can step up and down stairs with steady human foot trajectory.