The technology of magnetic suspension control is one of the key technologies of EMS maglev train. Aiming at the nonlinearity of the magnetic suspension system, a nonlinear controller was designed. Firstly a nonlinear mathematical model of the magnetic suspension system was derived under some reasonable assumptions. Then the model was linearized exactly by means of feedback linearization, and an equivalent linear model was developed. Finally the design of a nonlinear suspension controller was presented using state feedback based on the linear model. Results of the simulation show that the controller works better than the traditional controller based on the local approximate linearization, and has robustness against the disturbance of the gap and load.