Abstract: The evaluation of the critical speed is a basic subject in the rotor dynamics analysis, and its accuracy is very important. The simulation of active magnetic bearing (AMB)-test rotor for the HTR-10GT was presented, and critical speeds and models were obtained by using Samcef Rotor software. The relationship between the critical speed and the bearing stiffness was also analyzed. The conclusion can offer an important numerical basis for the design of the AMB control system.