ABSTRACT The oxidation of ammonium sulfite obtained from ammonia-based flue gas desulfurization by hydrogen peroxide in aqueous solutions was studied using a stirred reactor. An experimental study of the kinetic parameters of the oxidation process was investigated in the pH of 4.2–5.2 at 25–50°C. r = k 3 H + HS O 3 − H 2 O 2 is valid at sulfite concentrations of 10−4 mol/L for the pH range 4.2–5.2. At 298K and pH of 5.0, third-order rate constant k 3 was found to be (6.9 ± 0.21)×107 (mol/L)−2s−1. When the concentration of sulfite is 0.01 mol/L, the reaction first-order with respect to sulfite and hydrogen peroxide, and the second-order reaction rate constant at pH of 4.2–5.4 is lg k 2 = − 1.0135 pH + 7.4862 . Activation energy of E a = 32.26 kJ/moL. Kinetic data were compared with previous studies. A semi-empirical formula can express the effect of ionic strength on k 3. The kinetic data of ammonium sulfite oxidation with hydrogen peroxide have potential applications in the wet ammonia desulfurization process.