Abstract: In order to analyze the antioxidant activity of polysaccharide from sea cucumber and fermented sea cucumber by Bacillus natto, the hydroxyl radical scavenging ability, DPPH radical scavenging ability, ABTS radical scavenging ability and iron reducing ability were detected by spectrophotometry.The results showed that the hydroxyl radical scavenging ability and DPPH radical scavenging ability of polysaccharides from fermented sea cucumber were lower than those of polysaccharides from sea cucumber, but ABTS radical scavenging ability was higher than that of polysaccharides from sea cucumber, and both polysaccharides had no iron reducing ability.This study provided a scientific basis for the development and application of new type sea cucumber products.