Magnetic suspension cold compressor is one of the crucial components of the large superfluid helium refrigeration system. For the rotor system of magnetic suspension cold compressor，by constructing a finite element rotor model based on Timoshenko beam theory and defining the role of electronic control hardware as equivalent stiffness and equivalent damping，this study builds a completed magnetic suspension rotor model in the closed-loop system and completes the simulation calculation of critical speed and unbalanced response. The rigid body modal frequencies of the cold compressor rotor with the same PID controller，obtained by simulation and experiment，are 27 Hz and 28 Hz，respectively；and the percentage error of the first two critical bending modal frequencies does not exceed 2%. The rotor dynamic characteristics obtained respectively through unbalanced response simulation and the speed-up experiment within the rated speed range of 50 000 rpm，respectively，are consistent. It shows the modeling and dynamic calculation methods proposed in this paper are reasonable and reliable，which have essential reference significance for the cold compressor rotor’s structural design and controller commissioning.