crude glycyrrhizic acid (content 75%, gravimetric method; Content 30% ~ 40%,HPLC method) as raw material, neutralized in ethanol with potassium hydroxide. 100g of crude glycyrrhizic acid was added into 400mL of industrial ethanol and stirred at 40~50 ℃ for 1h. After suction filtration, the filter residue is extracted with 200mL industrial ethanol under the same conditions for 1h, the extracts are combined, and 20% KOH ethanol solution is added under stirring until the pH value of the solution is 7~8. After standing for a moment, 200g of potassium glycyrrhizinate yellow crystal was separated, put into 80~90mL of glacial acetic acid, heated to 75 ℃, and kept for a few minutes to convert it into single potassium salt. 40g (dry weight) of nearly white monopotassium glycyrrhizic acid salt was obtained by suction filtration, and washed once with a small amount of 95% industrial ethanol to remove flavonoids, glycyrrhetinic acid and other impurities. The crude product was dissolved in 400mL of ethanol glacial acetic acid mixture (200mL 95% of industrial ethanol +200mL glacial acetic acid), 10g of activated carbon was added, and decolorized at 80 ℃ for 0.5h. After filtration, the filtrate was placed into crystallization to obtain 25~30g of product with a yield of about 70%.