In order to reduce the temperature rise of the components of the totally enclosed fan cooling (TEFC) motor as much as possible and avoid the damage of the insulation structure caused by the excessive temperature rise, the influence of the cowling structure on the convective heat transfer characteristic of the TEFC motor housing surface is studied by numerical calculation method. Firstly, the temperature rise experiment is carried out on a prototype. The error between the simulated value and the experimental value of the winding temperature rise is 6.2% and the feasibility of the numerical calculation method is verified. Secondly, the necessary simplification of the threedimensional model of the prototype is made in the numerical calculation. The influences of the outer diameter of the cowling, the distance between the end face of the cowling and the end face of the fin, and the motor speed on the lateral average Nusselt number of the housing surface are studied emphatically. Finally, the results show that when the fin structure on the housing surface is fixed, there is an optimal value for the outer diameter of the cowling to make the convective heat transfer effect on the housing surface optimal. When the end face of the cowling is in contact with the end face of the fin, the lateral average Nusselt number of the housing surface is the largest. In addition, the convective heat transfer capacity of the housing surface increases with the increase of the fan speed.