Abstract:The antioxidant activities and the basic structural characteristics of polysaccharides from Dictyosphaerium sp.1A10 were studied.The crude polysaccharides from Dictyosphaerium sp.1A10 were extracted with ultrasonic-assisted extraction method and separated and purified by DEAE-52 and Sepharose CL-6B gel column chromatography.For the four purified polysaccharides，the 2，2-diphenyl-1-picrylhydrazyl（DPPH），2，2'-azinobis-（3-ethylbenzthiazoline-6-sulphonate（ABTS），hydroxyl（OH）free radical scavenging activities and the reducing ability were determined.The basic structures of the polysaccharides were analyzed by ultraviolet（UV）spectrometry，infrared（IR）spectrometry，high performance gel permeation chromatography（HPGPC），and high performance liquid chromatography（HPLC）.The results：（1）Four polysaccharide components of PC-1，PC-2，PC-3，and PC-4 were separated by DEAE-52 column chromatography，and PC-4 with higher antioxidant activity was purified by Sepharose CL-6B gel column chromatography to PCP-4.（2）Both PC-4 and PCP-4 had antioxidant activities.（3）The weight-average molecular weight of PCP-4 was 121 762 Da.PCP-4 carried pyranose and sulfate groups.PCP-4 was mainly composed of rhamnose，mannose，and galacturonic acid，with a small amount of glucuronic acid，glucose，and galactose.