Extraction method of hederagenin

The invention relates to an extraction method of hederagenin, and in the method, Chinese medicinal material teasel root is used as a raw material. The method comprises the following steps: a, adding hydrochloric acid or sulphuric acid into a 30-55% ethanol solution to prepare a 1.5-4N hydrochloric acid or sulphuric acid ethanol mixed solution; b, hydrolyzing the crushed teasel root in the hydrochloric acid or sulphuric acid ethanol mixed solution in the step a, filtering, and washing insoluble residues with water until the insoluble residues are neutral; c, extracting the residues obtained in the step b with an ethanol solution in a refluxing condition to obtain ethanol extract; and d, filtering the ethanol extract obtained in the step c through an ultrafiltration membrane with molecular weight cutoff of 3,000-8,000Da to obtain permeate, filtering the permeate with a nano-filtration membrane with a molecular weight cutoff of 200-600Da to obtain concentrate, and drying the concentrate to obtain the hederagenin. The method is simple and convenient in operation and simple and short in steps, so that the extraction quality and the extraction rate can be greatly improved.