Abstract: This paper designs a gait generation algorithm with 4 parameters for planar biped robots using virtual slope walking method.The relationship among the parameters is studied based on the existence conditions of virtual slope walking, and the independent parameters are reduced to 3.The final parameters are clear in physical significance and the walking velocity can be easily manipulated in real time.Experiments with the presented gait generation algorithm are made on planar robot Stepper,and continuous speed switch of 1.24-3.881egs/s is realized.