The research object was an oil cooled flat wire motor with a rated power of 230 kW used in a certain electric vehicle. A finite element model was established based on relevant parameters and loss analysis under high-speed operating conditions was conducted.Based on heat transfer,fluid dynamics and finite element method,simulation calculations were conducted on the original structure.The results show that the uneven flow rate and pressure at the front and rear fuel injection ports result in uneven distribution of the motor temperature field and large temperature difference.In response to the uneven spraying and large temperature difference of the front and rear fuel injection rings,the key structure and parameters of the cooling system were optimized through calculation and analysis.Then,the fluid and temperature fields characteristics of the optimized cooling system were calculated and analyzed,and compared with the structure before optimization.The results show that the optimized fuel injection ring has a more balanced velocity and pressure difference at the front and rear outlets,and the temperature difference between the stator and its winding at the front and rear ends is significantly reduced.The highest temperature decreases by 9.1%,and the maximum temperature difference decreases by 17.3%.The overall cooling performance of the motor system is significantly improved.