As a novel composite ceramic, B4C/Al has been widely used in the lightweight protective armour due to its excellent physical properties such as high hardness, high fracture toughness, and low density. In order to obtain the mechanical properties of B4C/Al composites under dynamic loading, the waveforms under different impact speeds and the fracture morphology with the split Hopkinson pressure bar (SHPB) testing and electron microscope scanning (SEM) has been performed, as well as the stress-strain curve characteristics and failure modes of the materials under different strain rates. Furthermore, the influence of Al content on the dynamic compressive strength of the material has analyzed. The results can provide reference for the design and application of B4C / Al composites.