The invention relates to a preparation method of a composite floor, in particular to a floor for a high-speed train, and belongs to the field of composite floor. The composite floor has a layered structure, and can be divided into five layers. A middle layer is a structure layer composed of an expanded vermiculite fireproof insulation board; the upper and lower layers of the structure layer are reinforced layers composed of stainless steel wire crimped mesh; fiber cement pressure plates are arranged outside the reinforced layers; and the surface of one fiber cement pressure plate is bonded with a rubber floor cloth. The structure layer of the floor adopts the light expanded vermiculite fireproof insulation board, which has fire resistance capacity at more than 1100 DEG C, fire performance reaching level A1, and is smoke-free and non-toxic during high temperature burning. The floor for high-speed train not only gains greatly improved fire retardant effect, and but also has the effects of heat insulation and sound insulation, especially reduced overall weight.