Abstract: In the experiment, lipid peroxidation of liver mitochondria was induced by Fe²⁺/Vitamin C in vitro and thiobarbituric acid (TBA) colorimetry was used to measure the effects of Stichopus japonicus crude polysaccharide (SJCP) on the content of malondialdehyde (MDA). And the chelating of Fe²⁺, the scavenging effects on reactive oxygen species (ROS) ((superoxide anion) O₂^-·, (hydroxyl radical)·OH, (hydrogen peroxide) H₂ O₂) and reducing power of SJCP were also determined.The results showed that SJCP had a very significant inhibitory effect on the increase of MDA (p < 0.01).When the concentration of SJCP was 0.333 mg/mL, the chelation rate reached 30.86%, and far less than the EDTA group. With the increase of SJCP concentration, the scavenging rate to three major mitochondrial ROS O₂^-·,·OH, H₂ O₂ were also gradually increased, and the reducing power was increased with the increase of dose, but weaker than the BHT group.It was indicated that SJCP could inhibit the lipid peroxidation of mitochondria to a certain extent, it had weak chelating ability to Fe²⁺, which indicated that SJCP could protect mitochondria through the mild anti-oxidation and removing ROS, so as to maintain the health of the body.