Objective To study the possible mechanisms of American ginseng capsules in prevention and treatment of rat liver injury induced by electromagnetic radiation. Methods Forty Sprague-Dawley rats were randomly divided into normal group

radiation group

silibinin group

and American ginseng group

with ten in each group.Except the normal group

the three rest groups of rats were exposed to electromagnetic radiation（ 900 MHz

370 μW /cm2）

4 h per day

for 12 days in a row. At the same time

the silibinin group and the American ginseng group rats were administered orally with silibinin capsules solution（ 7 mg / ml） and American ginseng capsules solution（ 19. 7 mg /ml） 1 ml/200 g every day respectively. And the normal group and the radiation group were given with equivalent normal saline. After 12 days

the rats were killed and liver ultrastructure was observed under transmission electron microscope. The content of malondialdehyde（ MDA）

the activity of glutathione（ GSH）

and the expression of phosphorylated vascular ataxia mutation protein（ ATM） and phosphorylated histone 2A variants（ γH2AX） in liver tissue were also detected. Results Compared with the normal group

the mitochondria and rough endoplasmic reticulum of liver cells mildly damaged

the content of MDA in liver tissue increased

the activity of GSH decreased

and the expression of ATM and γH2AX increased significantly in the radiation group（ P < 0. 01）. Compared with the radiation group

the mitochondria and rough endoplasmic reticulum of liver cells showed less damage

the content of MDA in liver tissue decreased

the activity of GSH increased

and the expression of ATM and γH2AX decreased significantly in the silibinin group and the American ginseng group（ P < 0. 05 or P < 0. 01）. Conclusion American ginseng capsules can improve the ultrastructure injury of rat liver induced by electromagnetic radiation. Its mechanism may be related to reduction of oxidative stress and the protein expression of ATM and γH2AX.