Based on the 3D Inverted Pendulum model,a new walking pattern synthesis was proposed,which can make a humanoid robot walk smoothly by variable ZMP(Zero-Moment Point).By the new way,in the single leg support phase,the COG(Center of Gravity) trajectory equation of the humanoid robot can be educed through the variable ZMP;while in the double leg support phase,the COG trajectory can be educed by the ZMP moving at a lower constant velocity.Simulation results verifies the proposed method,which can guarantee a relatively high stability.And the humanoid robot in this walking pattern can walk more smoothly,and in a more similar way to human walking.