Iodine-sulfur (IS) cycle is the most promising thermochemical water-splitting process for nuclear hydrogen production. The Bunsen reaction, which produces sulfuric and hydriodic acid for the two decomposition reactions, plays a crucial role for the continuous stable operation of the IS cycle. Insufficient kinetics studies on Bunsen reaction, particularly under the gas-liquid-solid heterogeneous conditions, have caused difficulties for the design of Bunsen reactor, as well as the optimization and improvement of the efficiency of the process. In this work, the reaction kinetics of gas-liquid-solid Bunsen reaction denoted in the pressure drop of SO2 was experimentally investigated, and the effluences of the main factors, including the initial SO2 pressure, molar ratio of I-2 to H2O, temperature, and stirring rate, were studied. In addition, a kinetics model for simulating the heterogeneous reaction was proposed and verified by the experimental data obtained under the three-phase Bunsen reaction conditions. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.