Plantago ovata Forsk has laxative and digestive effects,but due to its high viscosity,it is difficult to conduct systematic research on its polysaccharide components.Therefore,in this study,the low viscosity sulfated polysaccharide of P. ovata(POFP-S) was prepared by chlorosulfonic acid-pyridine method.,POFP-S was further separated and purified by DEAE-650M and Superdex 200 column to obtained a neutral and an acidic homogeneous polysaccharide (POFP-S1,POFP-S2),of which the POFP-S1 was mainly composed of rhamnose,arabinose,xylose,and glucose,with a molecular weight of 3 556 kDa and a degree of sulfate substitution of 0.364,while POFP-S2 was composed of arabinose and xylose,with a molecular weight of 833.7 kDa and a degree of sulfate substitution of 1.080.The characteristic absorption peaks in infrared spectroscopy (FT-IR) confirm the success of sulfation modification.The results of X-ray diffraction (XRD) and Congo red test show that both POFP-S1 and POFP-S2 have a triple helix structure,and with a crystalline and amorphous structure.This also indicates that sulfation modification does not affect the three-dimensional structure of the polysaccharides.The in vitro antioxidant activities of the sulfated polysaccharides were studied using DPPH,ABTS and OH free radical scavenging assays,and it was found that both POFP-S1 and POFP-S2 exhibited antioxidant activity.The results will provide a literature basis for further research on the structure and activity of polysaccharides from P. ovata,as well as the development of potential medicinal and food products and provide theoretical references for the study of high viscosity polysaccharides.