Abstract: Respective reactions of quinoline and isoquinoline with typical oxidative/reductive transient species, i.e., hydrated electrons, hydroxyl radicals, and hydrogen atoms (obtained after the reaction of an electron beam by proper condition-controlling) were investigated by pulse radiolysis. Absorption spectra of the transient products and their change trends were investigated. Reaction rate constants of hydrated electrons with quinoline and isoquinoline were 7.1×10⁹ and 3.4×10⁹ mol^-1·L·s^-1, respectively. The hydroxyl radical had rate constants of 7.2×10⁹ and 3.4×10⁹ mol^-1·L·s^-1, respectively. The rate constants of hydrogen atoms were 5.7×10⁹ and 3.6×10⁹ mol^-1·L·s^-1, respectively. Results showed that both quinoline and isoquinoline reacted with hydrated electrons, hydroxyl radicals, and hydrogen atoms very quickly. However, reaction rates of quinoline with these transient reductive/oxidative species were faster than that of isoquinoline. Stabilities of the transient products from these reactions were analyzed by electron theory. Reaction products from quinoline’s reaction with transient species were found to be more stable than reaction products from the isoquinoline reaction and this difference was the reason for the difference in rate constants.