The invention discloses a method for preparing a structural material of floors and coaches of high-speed trains. In the method, super light foamed aluminium or foamed aluminum alloy is used as a core layer and aluminum plates with different thicknesses, wherein the aluminum plates are used as upper and lower faceplates to be compounded with the core layer to form the sandwich panels. The method is characterized in that, through mechanically and forcedly paving and spreading the foamed aluminium core layer and the faceplates in a brazing filler metal melt and then carrying out fusion and vibration-assisted coagulation, attached surface oxidation films are removed, and the foamed aluminium core layer and the faceplates are prevented from being oxidized again during welding, and finally, a structural material for floors and coaches of high-speed trains which is compounded by carrying out large-area welding on the foamed aluminium core layer and the upper and lower faceplates. Compared with the material prepared by a traditional cementing method, the material prepared by the method disclosed by the invention has the advantages of high rigidity, long service life, noise isolation, energy absorption, vibration damping, inflaming retarding, corrosion resistance and electromagnetic shielding; meanwhile, the cold and heat processing such as re-welding, surface coating, scraping and thelike and the complete recycling of the material can be realized, and the prepared structural material can replace the structural material for floors and coaches of high-speed trains prepared from honeycomb aluminium sandwich structural slabs, honeycomb paper sandwich structural slabs, organic foamed plastic sandwich panels such as polyurenthane panels and the like, metal-coated wood boards, and other various composite materials.