Abstract: High-speed cutting machining quality and processing efficiency are closely related to the dynamics of a high-speed spindle system, and the rotating speed also has a significant effect on it. The paper firstly determines the impact factors of a high-speed spindle system, including the centrifugal force, gyroscopic moments and the bearing stiffness softening, etc. Then it builds the general spindle-bearing FEM considering high speeds. Taking a motorized spindle as an example, the effect of a centrifugal force, the gyroscopic effect, the radial stiffness and the coupling factors are analyzed qualitatively and quantitatively. Finally, the research shows that the variations of bearing radial stiffness, centrifugal forces and gyroscopic moments, have significant effects on the dynamics of a spindle system in high speeds. Thusly, when modeling a high speed spindle system, above factors must be taken into consideration.