To screen out the marine antioxidants with activity,we extracted and isolated four polysaccharides from Undaria pinnatifida,Porphyra,Sargassum fusiforme and Holothuria scabra through different polar solvents.The antioxidant activities of sulfated polysaccharide were determined via peroxide value (POV),polyphenol oxidase (PPO),and two free radical tests(DPPH·and O₂^-·).The results showed that four kinds of sulfated polysaccharides significantly inhibited the peroxidation of lard,scavenged free radicals in DPPH and superoxide anion system,and exhibited considerable antioxidant activities against PPO,with a certain concentration dependence.In conclusion,these four sulfated polysaccharides have the potential to develop into natural antioxidants.