Abstract: Due to the wide application of composites in impact protection, bulletproof, and explosion-proof fields, assessing their impact protection performance is key to structural design. This study proposes a fiber-reinforced composite and metal impact equivalence analysis method and evaluation system based on critical penetration velocity and energy absorption characteristics. First, an experimentally verified finite element (FE) model is used to analyze and compare the critical penetration velocity and energy absorption evolution mechanisms of two typical composites and metal plates under different impact velocities. Aramid and carbon fiber composites are used for comparison. Furthermore, based on the Lambert-Jonas (L-J) formula, a critical penetration velocity and energy absorption equivalence model is constructed for different materials. This reveals the equivalence law of metal and composite impact resistance with respect to thickness and surface density. Then, an equivalent model of critical penetration velocity and energy absorption between different materials was constructed based on the L-J formula, revealing the equivalence law of the impact resistance of metals and composites with respect to thickness and surface density. The results demonstrate that the proposed equivalent method effectively predicts critical penetration velocity and its equivalent relationship between metals and composites of different thicknesses. The critical penetration velocity prediction error is ≤6.8%. Through the impact energy equivalence criterion, the energy dissipation mechanism of composites and the plastic deformation mechanism of metals are incorporated into a unified evaluation system, providing a theoretical reference for the rapid comparative design of protective structures made of different materials.