An advanced structure containing cavities is adopted in distribution layers. A series of large-scale similarity-simulation tests are carried out on defense effect of the four structures for mass ammunition, and numerical simulations are developed by LS-DYNA software. The results indicate that the stress peak is distinctively decayed behind the cavities, and the defense effect of circular-section cavity is more effective than that of rectangle-section cavity. But because the transmission coefficient of stress waves of the structure increases, the defense effect is weakened when a thin steel plate is laid above the cavities.