In the series design of low speed high torque motor, the water cooled frame structure of axial water was adopted, considering the universality and the specification of the size of the frame. Through the calculation of the fluid field of the motor cooling system, the heat dissipation parameters of the motor were obtained. The temperature rise of the cooling water and the frame of the motor was obtained. The natural vibration frequency of the motor was obtained through the vibration mode analysis of the frame.