Energy of expansion ring/foam aluminum bumper can be absorbed through the elastic deformation, friction between the frustum and the expansion ring assembly thermal energy and aluminum foam compression deformation. In order to study the buffer energy absorption of the expansion ring/foam aluminum composite structure, the numerical simulation under high overload environment was carried out by ANSYS/LS-DYNA software, the buffer performance was evaluated by five indexes. The results show that the compressive mechanism is obviously different from that of a single expansion ring under high overload condition. Under the same displacement condition, the displacement curve of energy dissipation is obviously larger than the linear superposition of the single expansion ring structure and the foam aluminum displacement curve. Compared with the ring structure, the most prominent feature of the composite structure is that the buffer time is obviously increased.