Abstract: Purification conditions of the burdock root were studied with polysaccharide retention rate,protein removal rate and decolorization rate as the evaluation indicators. On the basis of single factor experiments,an orthogonal design was used to optimize the flocculation conditions from the polysaccharide solution. At the same time,compared with the traditional ethanol precipitation method,the purification effect of chitosan-based flocculation process and the antioxidant activity of the prepared samples were tested. Results showed that the optimum conditions were obtained as follows:The dosage of chitosan 1.2 mL/g,flocculation time 15 min,extract pH4.Under the optimum conditions,the extraction rate and the purity of polysaccharide were obtained as follows:40.01%±0.11% and 65.39%±0.67%,respectively. And the polysaccharides prepared by the chitosan-based flocculating purification were superior to that prepared by traditional method of the ethanol precipitation. In addition,in vitro antioxidant experiments showed that the polysaccharide prepared by the chitosan-based flocculating purification had a better ability to scavenge DPPH free radicals and to protect the oxidative damaged yeast. So compared with the traditional method of the ethanol precipitation,the chitosan flocculation method would be a better method to purify total polysaccharides from Arctium lappa L.