The invention discloses a calcium carbonate enhanced PVC composite board and a processing method thereof. The composite board comprises the following raw materials in parts by weight: 100 parts of PVCresin, 10-20 parts of calcium lignosulphonate, 40-80 parts of wood flour, 40-60 parts of modified calcium carbonate, 3-5 parts of aramid fiber, 3-5 parts of sepiolite fiber, 1-3 parts of polyether modified polydimethylsiloxane, 2-4 parts of polyoxyethylene glycerol ether monostearate, 1-3 parts of composite foaming agent, 2-4 parts of coupling agent, 1-2 parts of stabilizing agent, 2-4 parts of lubricating agent, 1-2 parts of antioxidant and 3-5 parts of processing agent. The modified calcium carbonate adopted by the invention is subjected to surface modification with ceraphyl RMT and polyoxypropylene polyoxyethylene propylene glycol ether and then is subjected to secondary surface modification with aminopropyl Poly(methylsilsesquioxane) and phytic acid. The PVC composite board prepared by the invention has the advantages of high strength, high toughness, high impact resistance, excellent fire resistance, wear resistance, heat resistance, difficulty in deformation, high stability, andthe like, and can be widely applied to the construction fields of wood floors, ceilings, wallboards, and the like.