Chemical kinetics of hydrogen production from the thermocatalytic decomposition (TCD) of methane at the early reaction stage and the steady state is modeled in this study. Numerical simulations are also carried out to figure out the detailed reaction phenomena in a catalyst bed which is packed with activated carbon. The effects of reaction (wall) temperature, catalyst mass, and reactant flow rate on the performance of methane TCD are evaluated. The predictions suggest that the CH4 conversion is linearly proportional to the reaction temperature at the early stage; the reaction is more sensitive to the reaction temperature at the steady state. Hydrogen formation from the reaction is also affected by the flow rate to a certain extent. In contrast, the performance of methane TCD is relatively insensitive to the catalyst mass, regardless of which reaction stage is. When the temperature distribution, reaction rate, and H-2 concentration in the catalyst bed are examined, two-dimensional contours of reaction rate are exhibited, whereas the isothermal and concentration contours are almost one-dimensional. The simulated results are able to aid in recognizing the reaction behavior in the reactor, thereby providing more detailed information to experimental measurements and practical design of reactor. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.