Abstract: In order to determine the reaction process and reaction mechanism of U(Ⅳ) produced by hydrazine reducting U(Ⅵ) with platinum as catalyst in the nitric acid environment, improve the reaction rate, and optimize the process flow, the effect of pH value on hydrazine bond breaking with Pt as catalyst was studied. The electron-spin resonance (ESR) method was used to study the mechanism of conversion of•NH₂ to•OH, and analyze the free radicals generated during the decomposition of hydrazine catalyzed by Pt in perchloric acid systems with different acidity for 0.25 mol/L and 0.5 mol/L hydrazine solutions respectively to determine mechanism for pH affecting hydrazine bond breaking. The results show that in the perchloric acid environment, the•OH detected in the Pt-catalyzed hydrazine decomposition reaction system is converted from•NH₂ produced by the decomposition of hydrazine. The acidity of the reaction system will affect the decomposition of hydrazine. During the process of decreasing acidity, the reaction rate of Pt-catalyzed hydrazine decomposition reaction will increase first and then decrease, and the decomposition reaction is the fastest between pH=1-2.