The invention relates to a preparation method for the supercritical anti-
solvent of water-soluble nano glycyrrhizic acid
powder, and is characterized in that: a CO2 high-pressure pump is started up to inject CO2 into a high-pressure crystallizing kettle by flow rate of 5-20L / h, the temperature of the high-pressure crystallizing kettle is kept at 32-75 DEG C and the pressure is kept at 7.5-25MPa to reach a supercritical state; absolute ethyl
alcohol with glycyrrhizic
acid content of 1-5mg / ml is sprayed into the high-pressure crystallizing kettle through a
spray nozzle with aperture of 20-1000um by flow rate of 1-30ml / min, glycyrrhizic acid
powder with
average diameter no more than 300nm is precipitated, and CO2 is continuously supplied into the high-pressure crystallizing kettle for at least half an hour to dry the formed nano glycyrrhizic acid
powder; and the
solvent, i.e. the absolute ethyl
alcohol, is separated from CO2 in a separation kettle with pressure of 5-6.5MPa and temperature of 25-50 DEG C, the absolute ethyl
alcohol is reused after the absolute ethyl alcohol is recovered, and CO2 gas is directly recycled. The invention has the advantages that the surface of the obtained nano glycyrrhizic acid powder is smooth, the size distribution is even, the water
solubility is good, no
residual solvent exists, the production technology causes no
pollution, the cost is low, the yield is high and the industrialization is easy.