High-temperature gas cooled reactor cooling medium drive motor is a unique driving equipment for coolant circulation in a reactor. The reliability of the motor is becoming increasingly vital to the stable operation of the reactor. To study the influence of the ventilation structure on the temperature distribution of a drive motor, the ventilation network model of the motor was developed using the fluid network method, the results of the ventilation system calculations were applied to the physical model as boundary conditions, and the temperature distribution was determined using the finite volume method. Meanwhile, two improvement schemes were proposed for the ventilation structure, and the influence of the ventilation duct geometrical dimension on the temperature distribution was investigated. Results show that the use of the proposed improvement schemes improved the utilisation rate of the coolant and reduced the maximum temperature of the motor by 5.7°C compared with the original structure. Furthermore, the validity of the calculation results was verified by comparing its results with test data. The maximum calculation error between the calculated results and test data was ∼9%.