Abstract: A high-power energy storage flywheel rotor system is taken as the research object to explore the dynamic characteristics of the flywheel rotor when the motor has initial static eccentricity. Firstly,the relationship between the unbalanced magnetic pull（UMP）and the eccentric displacement of the motor rotor is calculated using energy method. And then the electromechanical coupling dynamic model of the flywheel rotor considering UMP is established using the Timoshenko beam element model. Finally,the effects of the magnitude and direction of the eccentricity on steady and transient state dynamic characteristics of the flywheel rotor system are calculated and analyzed. The following conclusions are drawn that with the increase of eccentricity,a nested ring appears in the axial trajectory at the upper bearing,three frequency components appear in the spectrum diagram and their amplitudes increase,and the formant values of the acceleration response curve increase,while the critical speeds decrease. When the eccentric direction changes and the rotor rotates one circle,the amplitude of frequency components such as rotation frequency,the formant values of the acceleration response curve have obvious periodic changes.