The invention discloses a rail transit vehicle decoration floor composite material and a preparation method thereof, wherein the composite material is formed by sequentially compounding a lower panel,a glue film, a honeycomb core, a glue film and an upper panel from bottom to top, the upper panel and the lower panel are formed by curing a resin-impregnated fiber cloth, the glue film is a modifiedpolyethylene film, the honeycomb core is modified poly-p-phenylene benzobisoxazole fiber paper, and the modified poly-p-phenylene benzobisoxazole fiber paper comprises the following raw materials: poly-p-phenylene benzobisoxazole, a polypropylene resin, carbon fiber, esterified starch, a fly ash gel, hydroxymethyl cellulose, chitosan microspheres, graphene oxide, and a plasticizer. According to the present invention, the composite material for rail transit vehicle decoration floors uses the structure of the resin-impregnated fiber cloth-modified poly-p-phenylene benzobisoxazole fiber paper-the resin-impregnated fiber cloth, has high structural strength, further has advantages of light weight, high strength, water resistance, good compression resistance, no deformation and the like, and can improve the safety of rail transit vehicle decoration floors.