The invention discloses a cooling structure for a motor air cooler. The cooling structure comprises an upper mother board, a lower mother board and heat dissipation ribs connecting the upper mother board to the lower mother board, and further comprises cooling water pipes casted in the upper mother board and the lower mother board and water inlets/outlets integrally welded to the cooling water pipes. Each cooling water pipe is a two-layer circumferential or radial turn-back structure formed by bending a single metal pipe. The water inlets/outlets are arranged on the lower mother board. The upper mother board, the heat dissipation ribs, and the lower mother board are castings and are casted as an integrated member. When used, the motor air cooler is disposed on the cooling circuit of the cooling structure as needed. The cooling structure provided by the invention is not only easy to install, but also solves the low cooling efficiency of a split air cooler, and improves the heat dissipation performance of the motor. The cooling structure can be widely used in the field of high-power, high-torque-density and high-reliability motors with a high noise requirement, and is especially suitable for large-diameter motors.