For the high power density brushless DC motor of aircraft, a threedimensional thermal simulation model of motor and controller was established. According to the theory of heat exchange and heat transfer in the motor system, the internal heat transfer coefficient and boundary conditions were determined. Using ANSYS Workbench software, simulation and analysis were carried out for the temperature field of the established thermal model. The temperature field distribution and temperature curves of the motor and controller were obtained under different operating conditions. The results were compared with the experimental data. The accuracy of simulation was verified, which provided the basis for the design of the motor and controller as well as the calculation of the temperature field.