The invention relates to a method for reducing metallic aluminum from premelting slag in a VD (vacuum degassing) furnace. The method is characterized in that aluminum oxide in furnace slag reacts with carbon in a carburant by using the reduction-oxidation reaction of aluminum oxide and carbon under the high vacuum degree of the VD furnace so as to generate the metallic aluminum. The method has the advantages that the metallic aluminum is effectively recovered from the premelting slag in a process of using the premelting slag for desulfurization in the VD furnace, the treatment cost of molten steel is reduced, and the molten steel recovery aluminum adding amount can reach 0.003% to 0.020%.