Abstract: Negative Poisson’s ratio honeycomb structures, owing to their unique deformation and energy absorption characteristics, exhibit significant engineering application potential in aerospace, automotive, and impact protection fields. However, the Traditional 2D Star-shaped Auxetic Honeycomb (T2D-SAH) unit cell demonstrates only in-plane auxetic effects in the direction, and its sharp corners tend to cause stress concentration. To improve the above limitations, an Improved 3D Star-shaped Auxetic Honeycomb (I3D-SAH) unit cell was designed. The sharp corners of the T2D-SAH unit cell were replaced with cuboids and arranged in a circular array to form the I3D-SAH unit cell. The research methodology combining experiments and numerical simulations was adopted. The energy absorption performance of the I3D-SAH structure was compared with that of three different types of star-shaped auxetic honeycomb structures. The effects of geometric parameters and material properties on the energy absorption performance of the I3D-SAH structure under quasi-static compression were further investigated. The results show that, compared with the other three types of star-shaped auxetic structures, the I3D-SAH structure exhibits favorable performance in lightweighting, energy absorption, and load-bearing stability. In the investigation of geometric parameters, the effects of wall thickness t and oblique edge length l on most of the energy absorption performance indicators of the I3D-SAH structure show clear trends: as the wall thickness t increases, the compression force efficiency, mean force, and specific energy absorption increase, while the effective stroke ratio decreases; as the oblique edge length l increases, the densification displacement and effective stroke ratio increase, whereas the compression force efficiency, mean force, and specific energy absorption decrease. In the investigation of materials, aluminum alloy demonstrates better comprehensive performance compared with photosensitive resin and nylon. This study provides methods and technical support for the engineering application of the I3D-SAH structure.