Abstract: Hypersonic flight vehicles inevitably encounter extreme service environments characterized by the intense coupling of severe aerodynamic heating and mechanical loads. In this context, the Integrated Thermal Protection System (ITPS) has garnered significant attention due to its ability to seamlessly integrate thermal insulation and structural load-bearing functions, thereby meeting the urgent requirements for thermomechanical protection. However, existing research on ITPS remains largely confined to corrugated and pyramidal lattice sandwich configurations, resulting in a lack of in-depth investigation into the Body-Centered Cubic (BCC) lattice core, which exhibits superior mechanical properties, as well as the underlying mechanisms of its thermal insulation capabilities. To address this critical gap, this study designs six distinct ITPS configurations incorporating BCC lattice cores based on a multi-rotation strategy combined with a gradient filling strategy for insulation materials. Through a combination of rigorous theoretical analysis and comprehensive numerical simulations, the mechanical properties, heat transfer behavior, and thermomechanical coupling performance of these structures were systematically investigated. The results indicate that gradient-filled structures, owing to their relatively lower relative density, exhibit significantly lower critical aerodynamic pressure compared to uniformly filled counterparts. Notably, the structure with quadruple rotation and gradient filling demonstrated the lowest critical pressure. Additionally, the gradient filling strategy effectively reduces the temperature of the bottom panel and mitigates the thermal short-circuiting effect, thereby optimizing the internal temperature field distribution. Furthermore, the thermomechanical coupling analysis reveals that all six configurations exhibit consistent distribution patterns of stress concentration. Among these, the triple rotation and gradient filling modes significantly alleviate stress within the core struts. Simultaneously, the quadruple rotation structure displays the minimal displacement, demonstrating superior mechanical performance with overall deformation negligible enough to be ignored. The findings presented herein provide an essential theoretical reference and practical insights for the structural topology optimization and performance enhancement of integrated thermal protection systems intended for future hypersonic applications.