Abstract: The glycosaminoglycan was obtained by enzymatic hydrolysis from viscera of Ostrea rivularis. Its antioxidant activity was determined by hydroxyl free radical(·OH)and the 1-two phenyl-2-three nitrophenyl hydrazine free radical(DPPH)scavenging rate. The effects of different temperature,pH values,ultraviolet irradiation,NaCl concentration and simulated digestion of gastrointestinal on the antioxidant stability of glycosaminoglycan in Ostrea rivularis were investigated. The results showed that the glycosaminoglycan from Ostrea rivularis had good antioxidant activity in vitro. The scavenging rates of DPPH· and ·OH were 79.15% and 100.00%,respectively. Glycosaminoglycan from Ostrea rivularis still maintained good antioxidant activity under the conditions of 40~80 ℃,acidic environment,ultraviolet radiation,or Na⁺. In vitro simulated gastrointestinal digestion significantly decreased the antioxidant activity of glycosaminoglycan,but still had a certain scavenging ability. And the DPPH· scavenging rate was 26.43%,·OH scavenging rate was 10.07%. Therefore,the glycosaminoglycan of Ostrea rivularis has good antioxidant capacity,and it is a relatively stable natural antioxidant.