Permanent magnet brushless DC motors (BLDC) have the advantages of high power density, high operating efficiency, and are increasingly widely used in oil extraction, aerospace, and military industries. This paper designs a high-temperature BLDC motor, determines that its optimal slot and pole number combination is 9-slot/8-pole, the motor parameters are calculated using the rated parameter analysis method. Adopting the principle of fixed copper consumption, the stator size of the motor is optimized using genetic algorithm to achieve the maximum average torque. The finite element method (FEM) is used to optimize the no-load and load performance. The temperature field model of the motor is established, and the “magnetic-thermal” iterative coupling calculation study of the motor is carried out, the temperature rise characteristics of the motor in a 200 ℃ high-temperature oil well environment are analyzed, and the motor torque is compensated.