Through model establishment, grid partitioning, and solution settings (including boundary conditions, chemical reaction mechanisms, porous media and their heat transfer models, turbulence models, solution methods, etc.), numerical simulations were conducted on the thermal catalytic degradation of SF6 in a thermal catalytic reactor. The pressure distribution, velocity distribution, temperature distribution, and concentration distribution of various substances in the reactor were obtained. Pressure, temperature, gas flow rate, and substance concentration all exhibited inconsistency between the central axis and the wall surface. It was found that temperature had the most impact on degradation efficiency of SF6, uneven radial temperature distribution within the reactor lead to a decrease in SF6 degradation efficiency. Based on the analysis results, the optimization design of the reactor was carried out to solve the uneven distribution of the various parameters. The influence of gas flow rate and reaction tube inner diameter size on heat and mass transfer in the reactor was studied. Measures such as reducing reactor diameter and filling inert porous media components with high thermal conductivity were proposed to enhance heat transfer and optimize temperature field distribution to improve SF6 degradation efficiency. After adding porous media at both ends of the catalytic section, the temperature field, reaction rate and substance concentration distribution became more uniform compared to that before optimization. By studying the effect of inlet gas flow rate on reactor performance, it was found that too low or too high inlet gas flow rate can deteriorate effective utilization or heat transfer efficiency in the catalytic zone, resulting in uneven radial distribution of temperature field and reduced degradation efficiency of SF6. The optimal gas flow rate should be controlled between 0.4~0.8 m/s, which can balance the utilization, energy consumption and degradation efficiency of the catalyst. This study provides data support and theoretical guidance for the design, optimization, and practical application of SF6 catalytic degradation reactors.