In the actual operation of highspeed motorized spindle, there are problems such as high spindle heat and temperature rising inside the spindle, which lead to thermal deformation of the spindle and then affect the machining accuracy of motorized spindle. In order to solve the above problems, taking a certain motorized spindle as the research object, and the cooling ability of the cooling system was explored by combining simulation and experiment. The thermal characteristics of motorized spindle were described. The finite element simulation results of spiral and circulating cooling system were analyzed. The cooling ability experiment was carried out to verify the simulation results. The results show that the overall cooling effect and cooling rate of the spiral cooling system under steady state are better than that of the circulating cooling system. The results provide some technical references for the design, optimization and development of motorized spindle.