The paper presents a hybrid method for modeling the dynamics of the rotor system using the example of the spindle unit of a surface grinding machine. The method combines analytical and numerical calculation methods, combines theoretical modeling and results of experimental studies of this spindle unit. It is shown that the joint use of different calculation methods simplifies the modeling process and allows to obtain more complete information about the physics of the object functioning. In the considered example, analytical methods allow to see the relations between physical parameters of the model, and numerical methods allow to estimate the final dynamic characteristics of the rotor system. Since the damping parameters are determined with low accuracy, the rotor system is first modeled without damping and then the values of the modal damping coefficient from the experimental results are used. This approach allows to increase the accuracy of the rotor dynamics modeling.