The space debris problem has become one of the most pressing challenges in the field of space environment protection. Currently, most spacecraft shielding systems adopt Whipple-type structures, in which aluminum alloys are commonly used as bumper materials. In this study, the smoothed particle hydrodynamics (SPH) method implemented in the AUTODYN software was employed to numerically investigate the hypervelocity impact of spherical projectiles on high-entropy alloy (HEA) protective structures. The characteristics of the resulting debris clouds, including fragment number, mass distribution, and momentum, were systematically analyzed under various impact conditions. In addition, the effects of impact velocity and the ratio of bumper thickness to projectile diameter (t/D) on the hypervelocity impact response of HEA shielding structures were examined. The results show that, under identical impact conditions, the debris cloud characteristics generated by HEA protective structures differ significantly from those of aluminum alloy structures, namely: the total number of fragments increases by approximately 51.86%; the number of small-mass fragments increases by about 79.56%, while the number of large-mass fragments decreases; and the maximum debris cloud momentum along the impact direction (z-direction) is less than 75% of that associated with aluminum alloy structures across multiple projectile diameters. Parametric analyses indicate that the expansion of the debris cloud is primarily governed by impact velocity, with higher velocities leading to faster expansion, while the influence of the t/D is relatively minor. In contrast, the mass and kinetic energy of hazardous fragments (large-mass/high-energy fragments) are mainly affected by t/D, with higher values resulting in greater impact severity. These findings provide theoretical support and reference for the application of high-entropy alloys in next-generation spacecraft shielding structures.