Abstract: The chemical composition and biological activities of pure glycosaminoglycan from Patinopecten yessoensis waste were studied. The result showed that:the content of sulfate, uronic acid and amino sugar in glycosaminoglycan was 5.75% ±0.42% , 25.86% ±1.35% and 1.03% ±0.26% respectively. Glycosaminoglycan had a strong scavenging capacity of hydroxyl radical and a certain scavenging capacity of superoxide anion radical, but the effect was weaker than that of vitamin C. Glycosaminoglycan had strong inhibition on HepG2 cell, Glycosaminoglycan could extended the time of TT, PT and APTT in vitro experiment, but its activities were lower than that of heparin.