The invention relates to an aluminum-based amorphous/high-entropy alloy composite and a preparation method thereof, belonging to the field of metal composites. The composite is relatively low in density and high in compressive strength and has certain deformability. The preparation method comprises the steps of placing metal powder of Al, Cu and Ti or Al, Fe and Ti or Al, Ni and Ti into a ball milling tank, injecting methylbenzene from a glove box with an Ar atmosphere to the ball milling tank, taking all the components out of the glove box after sealing the tank, and carrying out ball milling to obtain aluminum-based amorphous powder; preparing an original material from Al, Co, Cr, Fe and Ni metal blocks, and carrying out alloy smelting in vacuum by taking Ar as a protective gas to obtain a mother alloy ingot of AlCoCrFeNi high-entropy alloy; atomizing the obtained mother alloy ingot, and screening to obtain spherical high-entropy alloy powder with the particle size of 20-100mu m; and after carrying out ball milling and mixing on the obtained aluminum-based amorphous powder and the high-entropy alloy powder, placing the mixture into a hard alloy die to sinter to obtain the aluminum-based amorphous/high-entropy alloy composite.