Effect of time dealy can’t be ignored, because of time delay’s objective existence in control system. As the new component, magnetorheological damper with quick response has been widely used. On the basis of analyzing time delay of magnetorheological damper and effect of time dealy on a single degree of freedom magnetorheological damper control system, it is proposed that magnetorheological dampers can be applied to highspeed locomotive control system. Theoretical studies is finished about time dealy problem in 1/4 locomotive system based on magnetorheological damper under active control strategy. And further discusses is given involving effect of time dealy on highspeed locomotive system under active control strategy. Simulations are included about effect of time delay on whole locomotive active control system.