This paper deals with the control of a single channel active magnetic bearing using sliding mode controller. First of all, mathematical model of a single channel active magnetic bearing are built and discussed in detail. The principle of sliding mode control stratery for an active magnetic bearing is then introduced. The design of a sliding mode controller is explained in order to realize stable magnetic levitation. Finally, to confirm the presented control method, a simulation model was carried out. The simulation results show that the magnetic bearing can work stably in one direction.