In order to satisfy the requirements of civil aircraft crashworthiness, a method of using aluminium foam as fuselage section filling material is proposed, and on this basis the energy absorption characteristics and impact response characteristics of fuselage structures filled with different relative densities of aluminium foam are investigated. Firstly, quasi-static and medium strain rate (0.001～100 s^–1) compression tests are carried out on aluminium foams with low, medium, and high relative densities, using an electronic universal testing machine and high-speed power loading systems. Secondly, an equivalent finite element model for different relative densities of aluminium foam is established and the validity of the model is verified by comparing the results of the model analysis with the experiments. Finally, the aluminium foam equivalent model is applied to the analysis of civil aircraft crashworthiness and the damage pattern, energy absorption, and acceleration time course of the fuselage section in the passenger cabin floor after placing aluminium foam of different relative densities are analyzed. The results show that the platform stress and volume specific energy absorption of the aluminium foam increase with increasing relative density, while the opposite is true for densified strain. The addition of aluminium foam-filled energy-absorbing structures better balances the energy absorption rate of the fuselage frame components than classic frame construction. At the same time, as the relative density increases, the energy absorption of the aluminium foam gradually increases and the peak acceleration of the cabin floor decreases, indicating that high relative density aluminium foam has a stronger cushioning and energy absorption properties than low and middle relative density aluminium foam, and these provide theoretical support for the application of aluminium foam to the crashworthiness design of civil aircraft.