The aim of the study was to investigate the relationships between apoptosis induced by radiation of electromagnetic pulses (EMP) and the expression of Smad4 in mouse spermatogenic cells. 40 adult Balb/c mice were used, and 20 were irradiated with whole-body 400kV/m EMP. The mice were sacrificed and specimens were harvested at 1, 7, 14, 21and 28 days after the irradiation. Histological changes were observed through Hematoxylin-Eosin staining (H-E staining), the apoptosis of spermatogenic cells was detected by terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling method (TUNEL method) and the Smad4 expression was observed using immunohistochemistry SABC methods. Severe injuries were observed 1day after the radiation and seminiferous epithelium was mostly recovered 28d after the radiation. The localization of smad4 was significantly different in EMP group compared to the control group, and the expression densities of smad4 decreased significantly at 7, 14and 21d after irradiation (,p,<,0.05). TUNEL assays demonstrated that there was a significant increase in the mean apoptotic index (AI) in irradiation groups than that of control groups (,p,<,0.01). The results suggested that Smad4 and TGF-β/Smad signal pathway might play an important role in spermatogenic cells apoptosis induced by radiation of EMP.