Foam materials of ZL104 alloy and 304 stainless steel fiber/ZL104 alloy composite were prepared by the infiltration casting method, and their pore structure, mechanical performance, sound absorption properties and the relevant mechanisms were investigated. The results show that within the prepared foam materials, there exist interconnected larger pores, and on the wall of which, there are many smaller sub-pores. The formation of such sub-porous structure may be ascribed to the effect of the second moderating salt adopted for the infiltration casting. Moreover, the fibers present in three states in the composite foam: pore wall fiber, perforated fiber, and inter-porous fiber. The typical composite foam with fiber diameter of 0.1 mm and porosity of 77-86%, while the mean diameter of 0.35mm for the main pores. The composite foam has better compression yield strength and sound absorption performance rather that those of the alloy foam with the same porosity. The compression and sound absorption properties of composite foams increased first and then decreased with the increasing porosity and fiber content. It is wealthy noted that among others the compression yield strength reaching the peak value of 2.6 MPa for the foam with porosity of 82% and fiber content of 5%, accordingly, the average sound absorption coefficient reaching the peak value 0.893 for the composite foam with porosity of 82% and fiber content of 8%, respectively. Finite element analysis shows that when being pressed, the pore wall fibers and perforated fibers can transfer and disperse stress, and the energy can be consumed by displacement and deflection of the fibers, thus enhancing the strength of the composite foam. J-A model analysis shows that the fibers protruded into the pores increase the surface roughness and specific surface area of the foam, resulting in an increasing acoustic wave loss of the composite foam, which is the reason for the higher sound absorption property of the composite foam.