Thermocatalytic decomposition (TCD) of methane in association with microwave heating is a route to produce hydrogen without the formation of CO and CO2. To recognize the interaction characteristics of methane TCD and microwave irradiation in an activated carbon catalyst bed, the chemical reaction along with microwave-assisted heating is modeled and simulated numerically. The influences of microwave power, volumetric hourly space velocity (VHSV), and catalyst bed geometry on the performance of methane TCD are investigated. The predictions suggest that a higher microwave power can efficiently promote the performance. Increasing VHSV reduces CH4 conversion because of the lower residence time of methane in the catalyst bed; nevertheless, more hydrogen is produced. A smaller diameter of catalyst bed facilitates the chemical reaction. The distributions of temperature, reaction rate, and electric and magnetic fields in the catalyst bed at various operating conditions can be clearly observed. Consequently, the developed method and predictions are able to aid in figuring out the reaction phenomena of experimental work and designing the reactor for achieving methane TCD. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.