<p>This paper investigates the dynamic response and failure mechanism of the double-layer M-shaped foldcore sandwich structure under low-velocity impact through experimental and finite element studies. Based on the length of the single-cell sawtooth platform, three different-sized hemispherical punches were used to conduct low-velocity impact experiments on two typical positions of the structure. The experimental results indicate that the larger the punch size, the greater the average penetration resistance encountered. The damage range of sandwich panels shifts from localized perforation to overall deformation. Furthermore, a three-dimensional progressive damage model for composite materials is established. Impact loading simulations are conducted in ABAQUS/Explicit for three different size punches, further examining the differences in load-bearing mechanisms between the two positions. Results indicate that the load-bearing mechanism of the V-shaped structure within the core undergoes changes when subjected to impacts from punches of varying sizes, whereas the load-bearing mechanism of the arched structure remains unchanged. This paper presents a series of experimental and simulation results, which can serve as a reference for the application of double-layer foldcore sandwich structures in the field of protection.</p>