Objective To study the radiation-protective effect of diallyl disulfide (DADS) in germ cells of male mice. Methods Male mice were whole-body exposured to 4 Gy X-ray irradiation to establish a animal radiation damage model. Testicular histology, sperm motility and sperm deformity rate were observed, protein carbonyl content, malondialdehyde (MDA) and 8-hydroxy deoxyguanosine (8-OHdG) content were tested to assess the degrees of radiation damages of sperm cells and protective effect of DADS. Testicular tissue antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-px) activity and glutathione (GSH) content were examined. The expression of Nrf2 signal protein was detected to explore the radiation-protective mechanism of DADS. Results Compared with the pure exposure group, the testicular tissue damages in the DADS pretreatment group were milder, sperm motility increased significantly ( P < 0.05) and sperm deformity rate decreased ( P < 0.05), and the protein carbonyl content, MDA and 8-OHdG levels significantly reduced ( P < .05). The antioxidant indexes of SOD, CAT, GSH-px and GSH were markedly improved ( P < 0.05), and the expression of Nrf2 was dramatically enhanced. Conclusions DADS has a protective effect on acute radiation injury in germ cells of male mice by means of anti-oxidative ability.