Aiming at the fact that it is difficult to exert the best performance of the spindle under different working conditions by adjusting the preload of the motorized spindle bearing, to realize the self-adjustment of the preload of the bearing, an intelligent adjusting component of the preload of the spindle with the advantages of strong adaptability, fast response, and high resolution is proposed. Based on the inverse piezoelectric effect of piezoelectric ceramics, the pre-tightening force regulating component of the spindle bearing is designed, and a finite element analysis model is established to explore the dynamic stiffness response of the spindle in the speed range. The thermodynamic model of the spindle is established, and the dynamic and thermal characteristics of controllable preload spindle under different working conditions are explored. The results show that the static measurement error of the control module is less than 2 N, which meets the requirements of spindle preload control. Within the range of the sweep frequency setting, the maximum displacement of the shaft end is 0.08 mm, and the dynamic stiffness of the spindle does not fluctuate significantly, which meets the design requirements. Compared with constant pressure preload, the active control method of spindle bearing preload based on the control module can reduce spindle vibration by about 13%. The bearing temperature can be effectively reduced by about 7 °C in the spindle’s middle and high-speed running range. The control precision of the control module meets the demand for intelligent adjustment of the spindle preload, which provides a feasible method for the intelligentization and multifunction of the motorized spindle of CNC machine tools and promotes the development of the motorized spindle of precision machine tools.