The invention relates to a preparation method of a kansui root active ingredient. The preparation method comprises the following steps: by adopting a two-dimensional liquid-phase chromatographic technique, taking normal hexane-ethanol as a moving phase and a normal-phase silica gel chromatographic column as a one-dimensional preparation chromatographic column, performing ingredient cutting on the kansui root extract, collecting the target ingredient as a one-dimensional separation ingredient, and then with X-Amide as a two-dimensional preparation chromatographic column, performing ingredient cutting on the one-dimensional separation ingredient, collecting, and performing rotary evaporation and concentration to obtain the kansui root active ingredient; the preparation process of the preparation method is high in repeatability and good in operability; meanwhile, the kansui root resources are rich and easy to gain; and in short, the preparation method conforms to the requirements of large-scale production.