Abstract: A parametric gait planning of 3D biped walking is proposed and a 13-rigid-body constrained dynamic model of humanoid robot is also established.With the considerations of six-point boundary constraints of successive and impact-less steps including SSP(single-support-phase) and DSP(double-support-phase),physical constraints of feasible gait and ZMP (zero moment point) stability constraints of locomotion,tow groups of slow and fast walking speed with smooth and nonjerky optimal joint trajectory curves to minimize integral quadratic amount of joint driving torques are obtained by adopting the parametric gait optimization approach,which makes the complicated joint trajectory planning problem transform into the optimization problem of limited parametric vectors composed of piecewise polynomial coefficients.The effectiveness of this method is confirmed by dynamic simulations and walking experiments on an actual humanoid robot.