Additive manufacturing is a highly effective process for producing intricate shapes, porous structures, and bionic configurations. Recently, the Ti-6Al-4V alloy has been employed to manufacture these porous and bionic structures, demonstrating commendable mechanical properties. In particular, functionally graded cellular materials (FGCMs) have garnered increasing attention due to their superior mechanical characteristics, such as enhanced energy absorption capacity. Compared to single porosity materials, the deformation-induced densification phenomenon in gradient porous materials has become a focal point. This layered densification during deformation results in superior specific energy absorption. However, not all gradient porous materials exhibit this deformation-induced densification, necessitating a thorough exploration of design criteria for further applications. Concurrently, predicting the energy absorption of gradient porous materials remains challenging, requiring a substantial amount of empirical data. To address these challenges and contribute to the field, this study investigates two types of porous/bionic structures, namely the Schon-Gyroid-sheet and Schwarz-Diamond-sheet. The objective is to elucidate design criteria for deformation-induced densification and establish an empirical rule for estimating energy absorption. Remarkably, the study proposes that the energy absorption of gradient porous materials can be approximated using the mechanical properties of single porous materials with analogous structures. This empirical rule facilitates the prediction of energy absorption for gradient porosity materials with diverse designs, exhibiting a minimal discrepancy (1-2%) between calculated and experimental energy absorption values