Abstract: Thin-walled tube of metallic shell is a sort of effective energy absorption structure and widely adopted in energy absorption systems. The energy absorption characteristics of square straight and tapered tubes subjected to axial impact are firstly studied with nonlinear finite element method in this paper. Some new designs of built-up structures like tapered, straight system with triggering feature are introduced, for improving the structural properties of energy absorption.Numerical results indicate that the absorption properties of built-up structures are highlighted when compared with the original.