The performance of the heating device in splice vulcanizers is a key factor affecting both the vulcanization quality and production efficiency of steel cord conveyor belts. To address the problem of non-uniform temperature distribution during the induction heating process of splice vulcanizers, a graphite heating plate was selected as the research object, and the influence of key parameters, including power supply frequency, heating plate thickness, coil-to-plate distance, and coil excitation current, on temperature uniformity was investigated. An electromagnetic-thermal coupled finite element model was established based on the COMSOL Multiphysics multi-physics simulation platform. Temperature standard deviation was adopted as the uniformity evaluation index, and multiple sets of parameter scans were carried out to construct parameter-response relationship curves. The Pareto front method was further introduced to analyze the trade-off between temperature uniformity and heating efficiency. The results show that, under the parameter combination of a power supply frequency of 18 kHz, a heating plate thickness of 12 mm, a coil-to-plate distance of 2 mm, and a coil excitation current of 24 A, the heating plate reaches 145℃ within 737 s, with an average temperature of 143.7℃, a maximum temperature difference of 4.4℃, and an average temperature difference of 1.3℃, which meets the uniformity requirements for industrial vulcanization heating. The experimental results are in good agreement with the simulation results. The conclusions provide a theoretical basis for the optimal design of induction heating devices in splice vulcanizers.