In order to identify unknown parameters of Bouc-Wen model for a ｍagnet orheological damper(MRD) and improve its generality in semi-active control, a kind of genetic algorithms(GA) is presented, the identification precision can be improved gradually by shrinking range of these parameters. Functional relationship between some parameters and applied current is also determined using curve fitting through analyzing their characteristic curves. The Bouc-Wen model for a MR damper is studied through numerical simulation method. These parameters are identified without any prior knowledge except for experimental data. After building a whole vehicle model with 62 degrees of freedom, numerical simulation analysis of semi-active control system is conducted to verify the Bouc-Wen model identified . Simulation results show that the semi-active control with Bouc-Wen model for MR damper whose parameters are obtained by GA can reduce lateral acceleration of car body and improve ride index of vehicle.