The invention relates to the field of boron carbide production and in particular to a preparation device for producing boron carbide. The preparation device comprises a furnace body, wherein the outlet of the furnace is connected with a crucible; a middle hole is formed in the central position in the bottom of the crucible; a disc-shaped base is arranged at the lower end of the crucible; a throughhole is formed in the middle of the disc-shaped base; a high-pressure water tube is arranged inside the disc-shaped base; a water outlet of the high-pressure water tube is formed in the inner side wall of the through hole; a high-pressure gas pipeline is arranged in the disc-shaped base; a gas outlet is formed in the inner side wall of the through hole; the gas outlet faces downwards in an inclined manner; a support base is arranged at the lower end of the disc-shaped base; a collection device is arranged at the lower end of the support base; and the bottom of the support base is connected with the upper end of the collection device through a bracket. The preparation device is reasonable in structure, novel in design, high in production efficiency and good in practicability, boron carbideof uniform powder can be prepared, the situation that the boron carbide is seriously consumed in multiple procedures is avoided, and the obtained boron carbide is high in purity.