The insulation space designed to mitigate the effects of a hightemperature gradient environment in high-temperature gas-cooled reactors is crucial for the normal operation of drive motors. This paper explores the insulation space's thermal suppression characteristics and dominant factors by employing the field and circuit combination method to simulate the fluidthermal evolution. It reveals the heat transfer modes and elucidates the mechanisms underlying thermal suppression behavior, enhancing model accuracy through experimental data integration. A thermal equilibrium assessment method is introduced, which constructs the spatial relationship of temperature parameters and the nonlinear mapping between environmental variables, structural parameters, and judgment criteria. Additionally, the response surface method is utilized to optimize the throughhole structure of the insulation space. Findings indicate that thermal convection primarily inhibits heat transfer within the insulation space in high-temperature gradient environments; both pressure and through-hole structure significantly influence the thermal state distribution characteristics. After optimizing the nonlinear structural parameters, the thermal balance performance of the insulation space was improved by 9.12% compared to the original model when the number of holes was 7 and the diameter was 66 mm, and the vortex situation in the insulation space watershed was effectively improved. This paper offers a foundational research basis and novel insights for the heat exchange system of high -temperature gas-cooled reactors, with broader implications for high -temperature motor system studies.