Abstract: The planning trajectory of humanoid robot bases on that some special sample points analysis during the biped humanoid robot walks,and compares with mankind itself walking gaits by observing and measuring the value of gaits,and also uses cubic polynomial interpolation to plan the trajectory of the biped walking humanoid robot in the course of walking,according to the height ration of human body,makes the walking posture of the biped robot more like human walking by calculating out a smoother and steadier walking trajectory.The result of simulation test indicates that the cubic polynomial interpolation method is a better way of planning trajectory of walking biped humanoid robot.Moreover the trajectory of interpolation function is smoother.