The invention relates to a method for separating lignin and cellulose from the wastes generated during the processes of extracting flavone, glycyrrhizic acid or polyoses from the traditional Chinese herb of liquorice. The method includes the following steps: (1) the waste residue of liquorice is added into the mixed solvent of methyl isopropyl ketone-ethanol-water and is manufactured into a turbid liquid; (2) the turbid liquid is treated by ultrasonic and then is stood for a certain period of time and filtered to obtain the filtrate and filter residues; (3) after the filtrate is condensed in vacuum and the solvent is recycled, a crystal is obtained; then the obtained filtrate is filtered and dried to obtain the lignin; the filter residues are directly dried to obtain the cellulose. The method for separating lignin and cellulose from the waste residue of the liquorice by utilizing the ultrasonic technology can overcome the defects of environment pollution and resource wasting caused by a soda boiling method and sulphite as well as the defect of high energy consumption caused by a high-boiling alcohol solvent method. The method creates a new approach for the comprehensive utilization of the waste residues of the liquorice.