. A new bionic biped walking mechanism (BWM) was put forward in this paper. Simple in construction, easy in control and droved by usual motor are all advantages of this mechanism. But disadvantage should not be ignored. Especially up and down bumpy of the centroid will influence the smoothness of the motion during walk. Through theoretical analysis of kinematics, motion characteristics and the movement of the spindle were obtained in a circle. To aim to bring down the uneven of the BWM, the relationship of all parameters was found and the scope of the fluctuation was established. In the end, all of the results were verified by simulation program of Matlab. The result provided theoretical guidance for optimal design of the mechanism in the further research.