Abstract: The active magnetic bearing （AMB） will be applied to suspend the turbine rotor and the generator rotor of the helium gas turbine in HTR-10. Since the rotaion speed of the turbine rotor under normal conditions is higher than that of two order flexible critical rotation speed, the control method of the AMB system should be explored to ensure that the turbine rotor can be well controlled. A small turbine rotor- AMB experimental system was built to study the control method, and the controller was designed by simulation and experiment. Using PID and phase compensation methods, two controllers were designed: one with low stiffness and the other with high stiffness. Controlled by these two controllers separately, the experimental turbine rotor can be suspended stably and its speed successfully increased higher than that of the two orderflexible critical rotation, which reached 450 r/s in maximum. Experiment showed that compared with lower stiffness controller, the vibration amplitude of the rotor reduced significantly under the action of high stiffness controller at 50~300 r/s. The experimental results indicate that the high stiffness controller has better performance than the low stiffness controller.