Abstract： Objective To investigate the protective effect of polysaccharides from sipunculus nudus on radiation injury in mice.Methods C57 mice were lavaged with polysaccharides from sipunculus nudus for 15 days and then had whole-body radiation exposure to 60Co γ (8 Gy). After that, the mice continued to be lavaged with polysaccharides once a day. Observations were made to see the survival of the treated animals 30 days after exposure, and WBC, SOD and MDA levels in the serum were monitored 3 days after radiation.Results Polysaccharides from sipunculus nudus could increase the 30-day survival rate and prolong the average survival time of the radiated mice. Polysaccharides from sipunculus nudus could also improve anti-oxygenation of the radiated mice.Conclusions Polysaccharides from sipunculus nudus had obvious protective effect on radiated mice and improved the anti-radiation capacity of mice