With the increase of spindle speed, heat generation becomes the crucial problem of high-speed motorized spindle. A new cooling system for motorized spindle is proposed based on the principles of thermoelectric refrigeration and fast heat conduction. The main strategy of the proposed ThermoElectric-based Cooling System (TECS) is using the ThermoElectric Cooler (TEC) to cool the spindle through a Heat Conduction Sleeve (HCS). The TEC is designed according to the heat generation of motorized spindle. The cooling capacity generated by the TEC is controlled by electric current passing through the TEC according to the temperature rise of HCS. The HCS is designed to distribute the cold quickly and is installed around the spindle sleeve working as cooling medium. The simulation results show that the cooling effect of the proposed TECS is better than water water-cooling system. It is meaningful to improve the accuracy of motorized spindle.