The invention relates to the field of preparation methods of silicon carbide nanowires. The preparation method of the silicon carbide nanowires described in the invention is as follows: placing oxygen-free carbosilane in a corundum crucible or a corundum boat, placing the corundum crucible or the corundum boat on a high-temperature resistant plate, and then pushing the high-temperature resistant plate into the high-temperature furnace, exhausting oxygen in the furnace, introducing inert gas at a rate of 6 - 15sccm for protection, raising the furnace temperature to 1000 - 1100°C at a rate of 5 - 15°C/min, holding the temperature for 1 - 3 hours, and then naturally lowering it to room temperature. The products obtained by the preparation method of the silicon carbide nanowires disclosed by the invention are all silicon carbide nanowires, the length is increased by two orders of magnitude compared with the silicon carbide nanowires prepared by the existing method, and the preparation method is simple, the raw materials are cheap and easily available, the equipment requirements are simplified, and the cost is low.