Abstract: The high-strength alloy steel-concrete composite structure exhibits extremely excellent protective efficiency in resisting the attack of penetrating weapons and is a highly promising protective structure form for the future. Aiming at the problem that the key mechanical parameters affecting the anti-penetration performance of alloy steel materials in the composite structure are not yet clear, this paper first conducts theoretical analysis on the correlation between mechanical parameters and anti-penetration performance, focusing on clarifying the action mechanism of strength and toughness during the projectile impact on alloy steel, and proposes a theoretical analysis criterion for the local penetration effect. Subsequently, taking the strength and impact toughness of alloy steel as the core mechanical indicators, 9 types of alloy steels with different strength-toughness combinations are prepared and selected to establish an experimental control group. On this basis, dynamic and static mechanical performance tests and comparative penetration tests are carried out. By comparing and analyzing the penetration test results of alloy steels with different mechanical properties, the key mechanical parameters influencing the anti-penetration performance of alloy steel are determined. The research results show that strength determines whether local penetration occurs in alloy steel, toughness ensures the structural integrity of the steel plate under impact loading, and the reasonable matching of the two is crucial for improving anti-penetration performance. Meanwhile, the key mechanical parameter indicators for the anti-penetration performance of alloy steel are proposed, namely, the yield strength of alloy steel should be greater than 60% of that of the projectile material, and the impact energy KU₂ should not be less than 50 J. This research achievement can provide theoretical basis and experimental support for the material selection and engineering design of high-strength alloy steel-concrete composite structures.