Preparation method for high-purity allantoin

The invention relates to a preparation method for high-purity allantoin. The preparation method comprises the following concrete steps: a) providing a solution formed by allantoin and hot water; b) adding an organic solvent into the solution; and c) carrying out recovery so as to obtain high-purity allantoin. The method provided by the invention can effectively remove impurities like allantoic, acid urea, glycoluril and biuret in allantoin and is suitable for industrial production.