The invention discloses a method for preparing a silicon carbide nanowire through vacuum sintering. The method includes the following steps that 1, Si and SiO2 are mixed to obtain a silicon mixture, and then the silicon mixture is mixed with graphene to obtain a mixed raw material; 2, the mixed raw material is put into a high-temperature vacuum sintering furnace, the interior of the high-temperature vacuum sintering furnace is vacuumized, then the high-temperature vacuum sintering furnace is filled with argon, then the interior of the high-temperature vacuum sintering furnace is vacuumized, and the process of vacuumizing, argon filling and re-vacuumizing is repeated at least 1 time; 3, the mixed raw material in the high-temperature vacuum sintering furnace in a vacuum state is sintered, the mixed raw material is heated to 1400-1500 DEG C from the room temperature within 2.5 h, then the temperature is preserved for 2 h, finally, the mixed raw material is cooled to the room temperature within 2.5 h, and the silicon carbide nanowire prepared through vacuum sintering is obtained. The method is high in preparation efficiency, and the shape of the prepared silicon carbide nanowire is good.