Based on online dynamic balancing, a novel parameter identification method is proposed for magnetic suspending rigid rotor system. Two unbalancing masses with given magnitude and phase were added to the rotor and used as a vibration exciter. The displacement stiffness and current stiffness were identified from the unbalancing response detected by the balancing monitor. The proposed method was experimentally validated with a magnetic suspending control moment gyroscope, and the displacement stiffness and current stiffness of its magnetic bearings were obtained within a certain rotational speed interval, which demonstrates the correctness and feasibility of the method. The experimental results show that the displacement stiffness and current stiffness decrease notably with the rotational speed increased for an outer rotor magnetic bearing.