Abstract: The contents of MDA in liver and liver mitochondria were studied by TBA assay in vitro,and the hemolysis extent of red blood cells and the swelling extent of liver mitochondria were detected by spectrophotometric method to evaluate the antioxidative effects of fucoxanthin from kelp Laminaria japonica in a lipid system of mice.The results showed that the fucoxanthin could inhibited the generation of MDA in liver and liver mitochondria under spontaneous or induced conditions.The swelling of liver mitochondria and the hemolysis of red blood cells were also inhibited with dose-response relationship,indicating that the fucoxanthin from the kelp had significant antioxidant activity.