Abstract: The optimum conditions for the extraction and separation of crude polysaccharide from yacon were studied in the paper. The crude polysaccharide was extracted by water. With extraction temperature, the ratio of material to solvent, extraction time, different concentrations of ethanol as influence factors, on the basis of single factor test, the orthogonal test was taken to study the optimum extraction and separation process of crude polysaccharide from yacon. Among the four single factors, extraction temperature had the greatest impact on the experimental results, followed by different concentrations of ethanol, the ratio of material to solvent, and the extraction time. The better conditions for the extraction and separation of crude polysaccharide from yacon were that the extraction temperature was 90℃, the final concentration of ethanol was 80%(v/v), the ratio of material to solvent was 1:20 g/L, and the extraction time was 2 h. Under these conditions, the extraction rate of crude polysaccharide was 5.11%, and polysaccharide content of crude polysaccharide was 46.2%.