This study presents a comparative investigation of typical X‑shaped structures to identify critical design parameters for passive vibration isolation. Several benchmark configurations are analyzed to evaluate the influence of key structural parameters on vibration isolation performance under different operating conditions. Theoretical analysis, finite‑element simulations, and experimental validation reveal that isolation performance is highly sensitive to the ratio between the horizontal displacement of the installed spring and the vertical displacement of the structure, which is nonlinearly coupled with other geometric and mechanical parameters. This ratio is identified as a critical and convenient optimization indicator for structural parameter selection in practical designs. The results provide new insights into the nonlinear dynamics of X‑shaped structures and offer clear guidance for their effective design and optimization in engineering applications.