Abstract: Electron spin resonance spectroscopy(ESR) was used to investigate the effects of hydrogen ion concentration and hydroxide concentration in perchloric acid system and sodium hydroxide system on the state and behavior of free radicals generated by hydrazine bond breaking catalyzed by catalysts. The difference of free radicals generated by Pt/SiO₂ catalyzed hydrazine decomposition in acid-base system was determined. The results show that in the alkaline system, with the increase of hydroxide concentration, the N-H bond breaking rate increases significantly, and the hydrolysis reaction is the main decomposition reaction. In acidic systems, with the increase of hydrogen ion concentration in the pH range from 6.9 to 1.1, the N-N bond breaking rate increases rapidly and is much higher than the N-H bond breaking rate. In the range of pH<1.1, with the increase of hydrogen ion concentration, both the N-H and N-N bond breaking rates decrease rapidly. In the process of acid-base change, the N-H bond breaking plays a leading role in determining the decomposition rate of hydrazine. With the increase of acidity, the N-H bond breaking rate decreases, and the decomposition rate decreases as well.