In order to reduce the temperature rise of high voltage induction motor and strengthen the convective heat transfer inside the motor, taking a high voltage induction motor with the rated power of 1 250 kW as the research object, a new rotor ventilation structure is designed based on computational fluid dynamics theory and convective heat transfer optimization. The three\|dimensional coupling analysis model is established to analyze fluid thermal coupling of the motor. With the help of digital simulation technology, the fluid flow and heat transfer characteristics of each ventilation duct of the motor under the ventilation structure of new and old rotors are calculated and compared. From the perspective of field synergy of convection heat transfer optimization, the temperature rise and temperature distribution of the motor under different rotor ventilation structures are obtained, providing a reference for the optimization design of the ventilation structure of high voltage induction motors. Finally, the temperature rise calculation results of the new motor structure are compared with the type test results of the prototype, and the temperature rise error is only 4%, which verifies the accuracy and validity of the calculation method.