The thermal decay characteristics of braking performance in eddy current retarders exhibit significant correlation with heat dissipation efficiency, wherein the rotor disc structural design directly impacts forced convection cooling effectiveness. Based on structural optimization principles, this study proposes an improved rotor disc configuration without modifying the base material or manufacturing processes. Through establishing a three-dimensional fluid-solid coupled heat transfer numerical model and validating via thermal load bench tests, we systematically analyze the influence mechanisms of blade configuration and quantity parameters on thermal dissipation performance. Results demonstrate that optimized blade geometry effectively enhances internal flow field characteristics, achieving 1.7 times higher outlet airflow velocity under typical operating conditions compared to the original design, while reducing the thermal decay rate of braking torque by 3.48%. This research provides both theoretical foundation and engineering implementation pathways for thermal management design in eddy current retarders.