Euglena gracilis was used as raw material. EGPS was separated and purified using DEAE cellulose colum and Sephadex G-100. EGPS1-A, EGPS1-B, EGPS3-A were obtained. On this basis, the purity identification and antioxidant activity of polysaccharide fractions were analyzed. The polysaccharides with better antioxidant activity were determined by molecular weight and monosaccharide composition. The purity identification results showed the purity of the three polysaccharides was high. Infrared detection confirmed that the purity of the three polysaccharides had characteristic absorption peaks of polysaccharides. The results of antioxidant activity showed EGPS1-A had the highest antioxidant activity among the three polysaccharides. The molecular weight of EGPS1-A was 136.8 ku and it consisted of 9 kinds of sugars such as mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, xylose, arabinose, fucose, and the composition ratios were 0.072:0.430:0.049:0.010:0.260:0.620:0.530:0.180:1.010.