Abstract: This paper presents an overall mechanism design for the biped walking-chair robot.New orthogonal joints used in the ankle joint and hip joint of the biped walking-chair robot make its mechanism simple and compact and improve accuracy in gait planning.A dynamics model of the robot is used to analyse the driving torque of each joint,and the driving power of motors are decided based on the analysis results.A damping system between the hip joint and the seat is considered and a model is proposed to analyse its effect on walking stability.Finally,a mechanical protector is designed for enhancing the safety of the passenger.