Abstract: OBJECTIVE To study the best protein removal process and monosaccharide composition of Polygala tenuifolia polysaccharide, and to preliminarily explore the neuroprotective activity of Polygala tenuifolia polysaccharide. METHODS The total polysaccharide of Polygala tenuifolia was extracted by hot water extraction. The best method for protein removal of total polysaccharide of Polygala tenuifolia was selected from four methods:enzyme method, Sevag method, enzyme-Sevag method and trichloroacetic acid(TCA)-n-butanol method. The method was optimized by response surface methodology to obtain the best process for protein removal of total polysaccharide of Polygala tenuifolia. Polygala tenuifolia polysaccharide was purified by ultrafiltration after protein removal. After complete acid hydrolysis of Polygala tenuifolia polysaccharide and derivatization by 1-phenyl-3-methyl-5-pyrazolone(PMP), the monosaccharide composition and proportion of Polygala tenuifolia polysaccharide were studied by HPLC. The protective effect of Polygala tenuifolia polysaccharide on PC12 nerve cells injured by H₂O₂ was studied. RESULTS TCA-n-butanol method was the best method for protein removal of Polygala tenuifolia polysaccharide. Through response surface optimization, the best process for protein removal of total Polygala tenuifolia polysaccharide by TCA-n-butanol method was TCA:n-butanol=1:7.5, Polygala tenuifolia polysaccharide solution:TCA-n-butanol solution=1:4.0, shaking time was 33.0 min. Polygala tenuifolia polysaccharide was composed of galacturonic acid, glucose, galactose and arabinose, and its molar ratio was 2.37:4.79:1:2.97. Polygala tenuifolia polysaccharide had no obvious toxicity to the proliferation of PC12 cells, and had protective effect on PC12 cells damaged by H₂O₂.CONCLUSION TCA-n-butanol method can effectively remove the protein of Polygala tenuifolia polysaccharide, which is composed of galacturonic acid, galactose, glucose and arabinose, and has neuroprotective effect.