Abstract: OBJECTIVE To investigate the radioprotective effect of Wuling bacteria fermentation bulk in mice. METHODS The delayed type hypersensitivity(DTH), proliferation and transformation of spleen lymphocytes, the level of serum hemolysin and lectin, and the carbon clearance capability were measured respectively in mice to determine the immune function. In addition, the hematological indexes, bone marrow cells, micronucleus rate of bone marrow cells and lipid peroxide MDA content in model mice with radiation injury were detected to determine the oxidative stress and hematopoietic function. RESULTS The results showed that, compared with the normal group, Wuling bacteria fermentation bulk at dose of 3 g·kg^-1 and 0.6 g·kg^-1 enhanced the DTH intensity(P<0.01), promoted spleen lymphocytes proliferation and increased clearance index, thymus index and HC₅₀ value(P<0.05 or P<0.01). Compared with the model group, the number of bone marrow nucleated cell and micronucleus rate of bone marrow cells in the Wuling bacteria fermentation bulk-treated groups showed no significant difference, but the content of MDA in serum and heart decreased significantly (P<0.05 or P<0.01), white blood cells increased obviously(P<0.01). CONCLUSION Wuling bacteria fermentation bulk could effectively regulate the radioprotective effect in mice by enhancing the immune and hematopoietic function.