Abstract: This paper presents a kind of method that first of all, an identification model of open loop system is obtained by using an area method of step response, then, the model of closed loop system by use of analysis of root locus of identification model of open loop system is carried out the synthesis. This method is applied to drive system of back wheel of THMR-Ⅱ and THMR-Ⅱ-A wheeled mobile robot. The step response of the resulting identification model of open loop system is consistent with the experimental curve of the practical system and one of closed loop system is consistent with one of that practical system satisfactorily.