Abstract: Objective To study the protective effect of Yiyuan oral solution against radiation injury in mice. Methods Yiyuan oral solution was administered in mice at 10.00,3.33 and 1.67 ml/kg for 30 days.The mice were then exposed to ⁶⁰Co-γ irra- diation at 3 Gy once and the effect of the irradiation on the WBC,bone marrow polychromatic erythrocytes (PEC) micronuclei and serum hemolysin antibody against sheep red cells. Results and Conclusion Yiyuan oral solution at 10 ml/kg significantly increased WBC counts,decreased bone marrow PEC micronucleus rate and enhanced serum hemolysin antibody in mice,suggesting the protective effect of this preparation against radiation injury.