The invention relates to a method for preparing high-purity scandium by means of neutralizing titanium white waste acid by the aid of calcium carbide residues at one step. The method includes steps of one-step neutralizing, filter-pressing, concentrating, impurity removing, extracting, acid dissolving, secondary acid dissolving and complex salt precipitating, oxalic acid precipitating, recycling and the like. The purity of obtained scandium oxide is 99.9-99.99%, and scandium element recovery is higher than or equal to 80%. The method has the advantages that scandium elements in the titanium white waste acid can be efficiently recycled and can be prepared under the condition of high purity, two types of waste can be recycled, the environment protection operation cost can be greatly reduced, a product, namely the scandium oxide, has huge market demand, is high in value, and accordingly the method has excellent social, ecological and economical benefits.