The methods for isolation and quantitative determination of dioscin, a spirostanol triglycoside, from the roots of Smilax china have been developed. Isolation of dioscin was achieved by silica gel and RP-18 chromatography. The HPLC method used for quantitative determination of dioscin enabled the standardization of the crude drug. It suggests that the content of dioscin in Smilax china should be above 0.01%.