Abstract: As the core component of high-precision CNC machine tools, the motorized spindle's thermal error caused by heat generation can seriously affect the machining accuracy of the machine tool. In order to improve the cooling efficiency of the motorized spindle, a double spiral cooling water channel was designed. Combining thermodynamic knowledge and fluid mechanics theory, a fluid-solid coupling analysis was conducted on commonly used series circulating cooling water channel, single spiral cooling water channel built-in to motorized spindle, and double spiral cooling water channel. The results show that under the same boundary conditions, the cooling effect of the series circulating cooling water channel and the single spiral cooling water channel is not significantly different, but the pressure drop of the latter is much smaller than that of the former, and the temperature of the heating surface is also more uniform. Compared with the single spiral water channel, the double spiral water channel has a maximum heating surface temperature reduction of 6.96℃, a temperature difference reduction of 6.91℃, a pressure drop reduction of 419.92 Pa at the inlet and outlet, and a symmetrical temperature field, further improving the cooling performance. The research results can provide reference for the design of cooling structures for high-speed motorized spindles.