Magnetically suspended control moment gyroscope (MSCMG) is a multivariable, strong coupling and nonlinear complex system. The vibration force is generated by multi-source disturbances such as residual mass unbalance and sensor error entering the closed-loop control system through different paths. The existing research work on dynamic modeling and harmonic vibration suppression of magnetically suspended rotor system is mostly based on the approximate linearization model of magnetic bearing force. When MSCMG outputs large torque, excessive rotor displacement runout will aggravate the nonlinear degree of magnetic bearing force, and seriously affect the suppression accuracy of harmonic vibration force of magnetically suspended rotor system. Therefore, it is necessary to establish a nonlinear dynamic model of magnetic bearing force and analyze its impact on the vibration force, and provide a theoretical basis for the research of harmonic vibration force suppression algorithm.