Abstract: Novel low-yield earth-penetrating nuclear warheads utilizing multi-point focused explosions pose a severe threat to deep underground structures. Addressing the critical challenge that traditional single-point simulations fail to replicate the synergistic damage effects inherent in such multi-point detonations, this paper innovatively designs and develops a vacuum chamber-based simulation test system for large-yield multi-point focused explosion cratering effects. The core innovation lies in the unique application of vacuum chamber technology, enabling efficient, cost-effective simulation of these complex phenomena with high result repeatability. Based on vacuum chamber explosion simulation theory, we established the similarity laws governing large-yield multi-point explosion cratering, determining key parameters including vacuum chamber pressure and simulated multi-source cavity pressure, while synchronization tests verified simultaneity across explosive sources. Referencing the US "Palanquin" underground nuclear test, we conducted vacuum chamber simulations for three-point sources under deep burial (4.3 kt, 85 m depth) and shallow burial (5 kt, 20 m depth) scenarios, comparing results with single-point explosion prototype data and empirical formulas. Results demonstrate that multi-point explosions significantly enhance crater radius, volume, and free-surface projection area compared to single-point events, dramatically expanding the damage zone, with explosive burial depth profoundly influencing the effect. This study pioneers a first-of-its-kind vacuum chamber multi-point explosion simulation system, providing an indispensable experimental platform and robust theoretical foundation for accurately assessing damage mechanisms and effectiveness of earth-penetrating nuclear multi-point strikes on deep underground engineering, holding substantial value for protective structure design and related engineering applications.