Abstract: As a critical ground-testing platform for aerospace equipment performance verification, the supersonic rocket sled requires its lower support structure to meet the requirements of lightweight design and high-precision testing under high-speed, heavy-load, and vibration service conditions, resulting in a pronounced trade-off between weight reduction and structural stiffness and strength. To address this multi-performance trade-off, this study develops a staged structural optimization workflow based on integrated multi-software simulation and topology optimization. First, several basic structural configurations are numerically pre-screened in MATLAB, and the isosceles trapezoidal configuration is selected as the preferred base configuration. Subsequently, parameter sensitivity analysis is carried out in ANSYS to identify a candidate inclination-angle range of 40°～48.39°. Representative configurations within this range are then subjected to preliminary topology optimization and mechanical response comparison, based on which 45° is selected as the base inclination angle for subsequent refined optimization. On this basis, topology optimization is performed in Altair Inspire with stiffness maximization as the objective and a design-domain volume fraction upper limit of 30%. The resulting material distribution is then interpreted to guide the engineering reconstruction of a manufacturable composite rib structure featuring a central web and X-shaped ribs. Finally, static structural and modal analyses are conducted in ANSYS to evaluate the static load-bearing performance and low-order dynamic characteristics of the optimized structure. After optimization, the structural mass is reduced from 2.9907×10⁵ kg to 1.5521×10⁵ kg, corresponding to a weight reduction of approximately 48.1%. Due to material removal and structural reconstruction, the maximum deformation increases from 1.761 mm to 3.734 mm, while the maximum von Mises stress increases from 13.53 MPa to 48.97 MPa. Nevertheless, the maximum stress remains far below the titanium-alloy yield strength of 930 MPa, indicating a considerable static strength margin. Modal analysis shows that the first six natural frequencies change from 48.752～101.850 Hz before optimization to 36.603～60.996 Hz after optimization, indicating that lightweight structural reconstruction has a significant effect on the low-order dynamic characteristics of the structure. The proposed workflow realizes the transformation from a theoretical topology-optimization result to a manufacturable structural design, achieving substantial structural lightweighting while maintaining adequate static load-bearing capacity and characterizing the low-order modal characteristics of the optimized structure, thereby providing an engineering reference for the design of supersonic rocket-sled support structures.