The invention discloses a calcium carbide furnace and a method for preparing calcium carbide. The calcium carbide furnace comprises an oxygen heat reaction zone, a calcium carbide reaction zone, an oxygen-containing gas spray umbrella, a material inlet, an oxygen-containing gas inlet, a tail gas outlet, electrodes and a calcium carbide outlet. The oxygen heat reaction zone and the calcium carbide reaction zone are arranged from top to bottom; the oxygen-containing gas spray umbrella is arranged in the oxygen heat reaction zone; the material inlet is formed in the oxygen heat reaction zone and is formed in a position above the oxygen-containing spray umbrella; the oxygen-containing gas inlet is formed in the oxygen heat reaction zone and is connected with the oxygen-containing gas spray umbrella; the tail gas outlet is formed in the oxygen heat reaction zone; the electrodes are embedded into the calcium carbide reaction zone from a furnace top of the calcium carbide furnace; the calcium carbide outlet is formed in the calcium carbide reaction zone. The calcium carbide furnace and the method have the advantages that oxygen-containing gas can be in sufficient contact with mixed materials, the mixed materials can be heated under combustion effects of partial carbon-containing materials, and accordingly calcium carbide production energy consumption and the production cost can be saved.