The iodine-sulfur (IS) process is one of the most promising thermochemical water-splitting processes for nuclear hydrogen production. The Bunsen reaction, which produces sulfuric and hydriodic acids for two decomposition reactions, plays a crucial role in the IS process. Insufficient kinetics data and models of the Bunsen reaction have caused difficulties for designing a Bunsen reactor and optimizing and improving the efficiency of the process. The mass transfer and kinetics mechanism of the Bunsen reaction, which is a complicated gas-liquid slurry process, were first analyzed and proposed on the basis of double-film theory and thermodynamics calculation, and intrinsic reaction rate equation models were deduced with different hypothesized reaction mechanisms. Then, the models were further improved, and the experimental kinetics data were used to verify the models. Finally, a set of reaction rate equations was developed, thereby confirming its reliability for calculating the reaction kinetics data. The built models for mass transfer and reaction kinetics provide crucial information for the thorough understanding of the reactor type, and designing the Bunsen reactor.