As one of the main heat generating parts of the high-speed motorized spindle, the built-in motor heat generated affects the rotational accuracy of the motorized spindle in actual working condition. In order to improve the cooling efficiency of the motorized spindle cooling water channel, a new butterfly wing bionic cooling water channel with double-layer wrapping characteristics was designed by combining the structural similarity theory with the reference of geometric model, structural function and configuration relationship of the micro-structure of morpho butterfly wings in nature. Based on the theory of fluid dynamics and heat transfer characteristics, the simulation analyses of fluid-solid coupling and conjugate heat transfer characteristics between the bionic cooling water channel and the original spiral cooling water channel were carried out. The results show that when the Reynolds number of cooling water and forced convection heat transfer area are the same, the cooling efficiency and flow characteristics of the bionic cooling water channel of the motorized spindle are better than those of the original spiral cooling water channel, the maximum temperature of the stator thermal boundary surface of the built-in motor is reduced from 8% to 11%. The maximum flow velocity of cooling water is 0.328 m/s and the maximum pressure drop at the inlet and outlet is 478.6 Pa, which has a good improvement in flow characteristics compared with the spiral water channel.