Abstract: In this paper, the dynamic deformation mode and energy absorption mechanism of aluminum foam sandwich circular tube under internal blast loading were analyzed by experimental, theoretical, and numerical simulations. A series of blast experiments were performed using spherical emulsion explosives of different masses. Three axially deformed regions were divided for the structure: a large plastic deformation region, a rigid section moving around the plastic hinge, and an undistorted region. An explicit calculation method for the dynamic response of aluminum foam sandwich circular tube under internal blast loading was proposed considering the circumferential plastic membrane forces and the axial moment components. The FE model, based on a 3D Voronoi algorithm for the foam core, was developed to investigate the energy dissipation distribution mechanism of the structure. Through the experimentally observed deformation mechanism of the aluminum foam sandwich circular tube under the internal blast loading, combining the bending deformation of the internal/external tubes and the foam core crushing, a theoretical solution for the energy absorption of the structure in the response process was given. The optimal solution set of aluminum foam sandwich circular tube was obtained by using the specific energy absorption and the mid-point deflection of external tube as control parameters. The effects of the explosive mass, the diameter and the wall thickness of the internal and external tubes, and the axial arrangement of the core on the dynamic deformation mode and energy absorption mechanism were further investigated. The result showed that the wall thickness of the internal tube has a greater influence on the mid-point deflection of the external tube, while the wall thicknesses of the core layer and the external tube have a smaller influence on the mid-point deflection of the external tube; If the sandwich circular tube with the axial distribution of foam cores decreases from the center to the edge gradient core, a better anti-blasting performance could be observed of the structure; Both the numerical and experimental results were consistent with the theoretical predictions.