The p-t curves of deuterium and tritium absorption by uranium were investigated at 150-300 oC by the reaction rate analysis in a constant volume system. The results show that the rate of tritium absorption is equivalent to the rate of deuterium absorption at the same temperature. However, the rate of tritium (deuterium) absorption is decreased when the tritium (deuterium) absorption temperature is increased due to the effect of contrary reaction namely desorption of uranium tritide (deuteride). The rate constants of deuterium and tritium absorption at different temperatures are determined and the activation energy value obtained by this analysis is (–42.8±0.3) and (–43.2±1.2) kJ·mol-1, respectively. Therefore, there are not remarkable kinetic isotope effects for deuterium and tritium absorption by uranium.