Remaficable development of transport has caused severe and many-faceted requirements for safety and environment issues and consequently has made a lot of progress in the perfoimance and weight reduction of shock absorber. The honeycomb stiucture crushes with the flat load time histoiy and with the long stroke in the axial direction so that it is a suitable energy absorber wirile it is preferably used as a core material of the sandwich panel because of its high specific strength. In this study, the axial crushing behavior of aluminum-alloy honeycomb was investigated to evaluate its energy-absorbing ability (mean buckling stress or absorbed energy per unit volume) with laying emphasis on the geometric effect by using the explicit FEM code LS-DYNA The calculated results were compared with those obtained by some theories, wiiich give the respective formulas for mean bickling stress as functions of the ratio of thickness to side length of regular hexagon, and the effects of inertia and strain rate on the energy absorption ability were also discussecL