Abstract: To verify the theoretical results of dynamic walking and satisfy the economy requirements,this paper designs and implements a planar footless biped robot THR-I based on bus servo motor.Firstly,the configuration of the robot,including mechanical design and control system,are introduced.During the establishment of walking dynamic equations,the coupling effect of central constraint system is considered.Secondly,walking constraint is designed based on virtual constraint principle,and fast dynamic walking with the period of 0.64 s and the step of 0.56 leg length is successfully realized.