Abstract: Effects of temperature and bentonite density on the sorption distribution coefficients and apparent diffusion coefficients of ~(99)Tc in compacted bentonite are studied by using capillary method. The results fit the Fick’s second law very well and are in good agreement with the literature data under (similar) experimental conditions. The results indicate that apparent diffusion coefficients and sorption distribution coefficients of ~(99)TcO~-_4 in compacted bentonite decrease with the increase in bentonite density and increase with the increase in temperature. Temperature and the compactness of bentonite, i.e., the porosity of compacted bentonite, contribute significantly to the migration and sorption of (radionuclides) in compacted bentonite.