The article presents an FEM model of the spindle system, in which angular contact ball bearings with active preload control are used. This model allowed to determine the frequency and form of natural vibrations of the system. The model was prepared using the Abaqus programming environment. Various bearing preload states were adopted during the tests. It has been shown that the spindle system is sensitive to changes in the stiffness of bearing supports. Tests using models were then verified on a real stand. First of all, using the external excitation from an electromagnetic exciter, the frequency range of resonance vibrations of the spindle system was determined. Then the amplitude - frequency characteristics of the tested spindle were determined at various bearing preload values. A general operation scheme of the control system for the active change of the preload value of the angular contact ball bearings during the work of the spindle system was proposed.