The invention discloses a method for recovering carbon from waste cathode carbon blocks of electrolytic aluminum. The method mainly comprises the following steps of: crushing, grinding, leaching in water, floating, and the like. The method has the advantages that the carbon content of recovered powdered carbon reaches higher than 70 percent, and the carbon recovery rate reaches higher than 98 percent, thus the recovered powdered carbon can be used for preparing carbon materials for aluminum electrolysis, aluminum oxide desulfurizing agents, and the like; and the method has simple process, low production cost, no secondary pollution, stable and reliable product quality and high yield, can realize continuous scale production and is beneficial to environmental protection.