A special three phase asynchronous motor applied to top drive facility was studied, which uses the compulsorily ventilation and nonstandard design. Critical techniques, such as nonbase design, ventilation hole of stator iron yoke, epoxy resin sealing at stator winding end, and squirrelcage rotor composed of copper bars were adopted, which satisfy the strict requirements under the condition of frequent start and stop, overloading, and saltmist. Temperaturefluid field coupling model was established, and then the transientstate temperature trends and steadystate temperature distribution of the parts of motor under the rating condition were analyzed. The results of simulation and thermal rising test showed that the temperature in the axial direction was higher at the locations of the posterior segment, and testify that the temperature distribution has no local hot spot. At the same time, experiment verifies that the temperaturefluid field coupling model and result are reasonable, which satisfy the requirement of H level temperature rise. The effect of inlet pressure and ventilation hole diameter change on temperature rise were analyzed on the basis of coupling model, which provides the theoretic foundation for improving cooling structure of motor.