Abstract: Response surface methodology( RSM) was applied to optimize the extraction conditions of water- soluble polysaccharides from lotus root. The physicochemical properties of polysaccharides were then analyzed. Three independent variables,extraction temperature,extraction time and shearing speed,were chosen to establish the quadric regression equation for predicting the yield of polysaccharides. The optimum extraction conditions were obtained as follows: extraction temperature 89 ℃,extraction time 121 min and shear speed rate 11800 r / min,which led to estimated and observed values of maximal yield of polysaccharides of 5.64% and 5.88%,respectively.Crude polysaccharides extracted from lotus root were purified by Sevage method.The purified polysaccharides showed a stronger DPPH radical scavenging activity compared with the crude ones. Their molecular weights were less than24.2 ku and mainly composed of pyranoid monosaccharides.