Objective:To study the protective effect of yam polysaccharides on immune system damage induced by continuous low-density microwave radiation in mice. MethodsICR male mice were randomly divided into 5 groups: blank control group, radiation injury group, and low-, medium- and high-dose yam polysaccharides groups (200,0 and 800 mg/kg). Except for the blank control group, mice in the other groups were exposed to microwave radiation at 10 mW/cm,2, 5 min/d for 30 consecutive days to establish the mice model of continuous low-density microwave radiation. Starting from day 21 of radiation, the mice in the low-, medium- and high-dose yam polysaccharides groups were orally administered with yam polysaccharides at 200,0 and 800 mg/kg respectively, and those in the blank control group and the radiation injury group were given distilled water of equal volume. All of the animals were treated for 10 consecutive days. Relevant indicators of cellular immunity and humoral immunity, including thymus index, spleen index, macrophage phagocytosis index, T lymphocyte proliferation rate and the serum levels of IgG and IL-4 were determined.  Results:Compared with the blank control group, spleen index, macrophage phagocytosis index, T lymphocyte proliferation rate and the serum level of IgG decreased and the serum level of IL-4 increased in the radiation injury group, with significant differences (P,<,0.05, P,<,0.01). Compared with the radiation injury group, macrophage phagocytosis index, T lymphocyte proliferation rate and the serum level of IgG increased and the serum level of IL-4 decreased in the yam polysaccharides groups (P,<,0.05, P,<,0.01).  Conclusion:Yam polysaccharides significantly improve the impaired immune system function induced by continuous low-density microwave radiation in mice.