Abstract: The physical and chemical properties of GMZ bentonite will be changed by irradiation from high level nuclear waste after long time deep geological disposal. In this study, the diffusion behaviors of Re(Ⅶ) in 1 MGy irradiation montmorillonite and bentonite were investigated by a through-diffusion method at pH=3.0 and 10.0. The results were also compared with the unirradiated montmorillonite and bentonite. The effective diffusion parameter D_e and accessible porosity ε_acc were obtained. The results show that D_e and ε_acc are (1.00-1.49)×10^-11 m²/s and 0.09-0.14 at pH=3.0, while D_e and ε_acc are (1.50-2.10)×10^-11 m²/s and 0.07-0.11 at pH=10.0, respectively. D_e and ε_acc remained unchanged with the increase of pH, which indicates that pH has insignificant effect on Re(Ⅶ) diffusion. In case of montmorillonite, D_e of irradiated clay is lower than that of unirradiated one, whereas, it is higher than that of unirradiated bentonite. It is probably because of that the component of bentonite except montmorillonite may change by the γ-irradiation. The increase of ε_acc indicates that the diffusion path of Re(Ⅶ) is broaden. However, γ-irradiation has no obvious effect on D_a because of the minor change of both D_e and ε_acc. Moreover, the relationship of D_e and ε_acc can be described by Archie’s law with exponent n=1.7-2.4 for ReO^-₄.