Abstract: In order to meet the requirements of axial displacement measurement and suspension of the spherical rotor of spinning rotor gauge in a vacuum, an AC-DC coupled frequency domain model based on AC bridge structure is established for its magnetic levitation system loaded with both levitating DC current and eddy current sensor AC excitation. The fourth-order Runge-Kutta method is used to calculate the displacement response of the levitation process. The results show that the loading of the AC excitation introduces nonlinear factors into the magnetic levitation system. According to the above consideration, the eddy current sensor with the air magnetic core is fabricated and the measurement circuit is designed. The influence of the eddy current generated by AC excitation on the magnetic levitation system of the spinning rotor gauge is analyzed experimentally. The influence of the AC action is controlled by optimizing the coil radius parameters. The influence on the AC action is realized by optimizing the coil radius parameters, which provides theoretical guidance for the optimal design of the magnetic levitation rotor vacuum gauge.