The aim of this study was to explore the protective effects and possible mechanism of Eucommia ulmoides Oliver leaves extraction on acute injury induced by carbon ion beams in mice. The Kun-Ming mice were fed orally with crude extracts of Eucommia ulmoides Oliver leaves in various doses for 7 days, whole bodys were then irradiated with 6Gy 12C6+ ions, the liver and lung tissues of mice were collected at 12 h after irradiation. The activity of superoxide dismutase (SOD) and the content of Malondiadehyde (MDA) in liver and lung tissues were detected by the xanthine oxidase method and the thiobarbituric acid (TBA) reaction chromometry, respectively. Meanwhile, the DNA injury was determined by single cell gel electrophoresis (SCGE, comet assay) and the apoptosis was assayed by flow cytometry method. The results showed that there were dose-related significant decreases in MDA level, percentages of apoptosis cell, tail moment rate of cells and tail length in each concentration groups of drug. The dose-dependent marked increment of SOD activity in pretreated with drug groups compared with irradiation only groups. The extraction of Eucommia ulmoides Oliver leaves could greatly reduce the DNA danage and inhibite the cells apoptosis of irradiated mice. It can be deduced that the extraction of Eucommia ulmoides Oliver leaves can protect mice from the radiation damage due to its dramatic capacity scavenging free radical.Cited