A new detailed kinetic modeling was developed for homogeneous decomposition of hydrogen iodide (HI) in the sulfur-iodine cycle. Results show the HI decomposition reaction is sensitive to temperature, and the response time of reaction reduces from 1 s to 10 ms as temperature increases from 500 to 800 degrees C. The decomposition is also improved as pressure increased. Kinetic calculations are also compared with the experimental data, and all trends of the experiment can be reproduced by the model. Sensitivity analysis shows that the reactions of HI with HI, H and I play a major role in the hydrogen production process and the hydrogen consumption occurs primarily by reaction of H with 12 and reaction of I with H-2 to form HI. As temperature increases, different reactions play a dominant role in HI decomposition process. Based on the detailed kinetic modeling and sensitivity analysis results, the HI decomposition reaction path diagram was constructed in this paper. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.