The yam polysaccharide was extracted from Tiegun yam (Dioscorea opposita Thunb.cv.Tiegun) by water-alcohol-precipitation method. The influence of the factors, extraction temperature, solid-liquid ratio, extraction time and ethanol concentration on the crude polysaccharide yield by single factor and orthogonal experiment L9(34) was studied. The result showed that the optimal parameters were as follows: extraction temperature 90 ℃, extraction time 2.5 h, ethanol concentration 75% and solid-liquid ratio 1∶6(W∶V). The crude polysaccharide yield was 6.77%. Among the factors the extraction temperature was the biggest one to affect the polysaccharide yield