Abstract: The catalytic reaction kinetics of U(Ⅵ) with hydrazine on platinum black in nitric acid media was studied. By investigating the influence of U(Ⅵ) concentration, hydrazine concentration, acidity and catalyst amounts(r_S/L) on the reaction, the reaction rate equation is obtained: -dc(UO²⁺₂)dt=kc^0.44(UO²⁺₂)c^0.19(N₂H⁺₅)c^-0.23(H⁺), and the rate constant is 2.6×10^-3 (mol/L) 0.6/min at 60 ℃ and r_S/L=2.0 g/L. The effect of temperature was also investigated. The results show that the temperature accelerates the reaction and the reaction process changes from kinetics-controlled process to diffusion-controlled process. Comparing nitric acid with perchloric acid, it is found that the reaction rate in nitric acid is obviously lower than that of perchloric acid.