Abstract: The diffusion behavior of))~99)TcO~-4 and HTO in granite slice samples is investigated by laboratory simulation method. The apparent diffusion coefficients of))~99)TcO~-4 and HTO in the granite are obtained. In comparison, the relation of the apparent diffusion coefficients of))~99)TcO~-4 and HTO in the granite and the diffusion coefficients of some other nuclide species in granites reported by other scientists to the inverse ratio of the square root of their molecular mass is analyzed. The analysis indicates that for the main species of some wealky absorbed nuclide species, such as))~99)TcO~-4,HTO,~125)I~-,~36) Cl~- et al., the ratio of the apparent diffusion coefficient seems to be inversely related to the ratio of the square root of the molecular mass.