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The control of mechanical energy loss is especially key in the design of permanent magnet drive motors for special vehicles. This paper takes a 300 kW high-efficiency motor as an example, and under the operating condition of 9000 rev/min, in order to control the size of the mechanical loss <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>P</mi></mrow><mrow><mi>m</mi><mi>e</mi><mi>c</mi><mi>h</mi></mrow></msub></mrow></semantics></math></inline-formula>, improve the efficiency of the motor, as well as enhance the ventilation and heat dissipation performance of the motor, the structural parameters of the motor’s Axis fan are identified by using the Reverse Engineering (RE), and the fan performance is simulated and analysed by using the standard k-ε turbulence model of Computational Fluid Dynamics. The mechanical loss calculation model is investigated, and the effects of different blade numbers, wrap angles, and mounting angle parameters of the fan on the mechanical loss <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>P</mi></mrow><mrow><mi>m</mi><mi>e</mi><mi>c</mi><mi>h</mi></mrow></msub></mrow></semantics></math></inline-formula> are derived. And finally, the scheme is calculated to show that when the blade number Z is 13, the wrap angle <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi mathvariant="sans-serif">Δ</mi><mi>φ</mi></mrow></semantics></math></inline-formula> is 60°, the front mounting angle <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>Φ</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></semantics></math></inline-formula> is 45°, and the rear mounting angle <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>Φ</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></semantics></math></inline-formula> is 30°, the mechanical loss <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>P</mi></mrow><mrow><mi>m</mi><mi>e</mi><mi>c</mi><mi>h</mi></mrow></msub></mrow></semantics></math></inline-formula> decreases from 8.0 kW to 2.54 kW, and the motor efficiency <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>η</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></semantics></math></inline-formula> is greatly improved, increasing from 94.2% to 96.1%. Meanwhile, based on finite element simulation experiments, the effects of the motor Axis fan on the steady-state temperature field of the pre-optimised and post-optimised fans are compared, and the optimised axis fan makes the motor ventilation and heat dissipation more reasonable. The maximum temperature of the motor under the same working condition decreased by 16.7 K, the efficiency <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>η</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></semantics></math></inline-formula> of this motor was greatly improved, and the efficiency <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>η</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></semantics></math></inline-formula> increased from 94.2% to 96.1%.