The invention discloses a method for preparing carbenoxolone sodium, which comprises the following steps: using a compound of glycyrrhetinic acid and succinic anhydride as a reactant, using 1,1 - dichloroethane or chloroform as a reaction medium, and using triethylamine or 4 - dimethylamino pyridine as a catalyst to obtain a crude product; and allowing the crude product to be subjected to recrystallization, adding alkaline and water to adjust a solution to be alkalescent, and separating impurities from carbenoxolone sodium. According to the method provided by the invention, the amount of the used reaction medium is less, water is used in a purification process, the reaction time is short, and the purity of the product carbenoxolone sodium is more than 97%.