Hydrogen production and thermal behavior of methanol autothermal reforming (ATR) triggered by microwave heating are studied. Methanol steam reforming (MSR) is also investigated for comparison. A commercial Cu-Zn-based catalyst is used. The gas hourly space velocity (GHSV) is fixed at 72,000 h(-1), and the reaction temperature and the oxygen/methanol molar ratio (i.e. O-2/C ratio) are in the ranges of 250-300 degrees C and 0-0.5, respectively. The results suggest that an increase in O-2/C ratio or reaction temperature diminishes the supplied energy for microwave irradiation, as a result of more oxidative reactions involved. However, the performance of methanol ATR at 300 degrees C is lower than that at 250 degrees C. The methanol conversion of ATR is beyond 90% at O-2/C = 0.125 and 0.5, whereas it is relatively low (56-67%) at O-2/C = 0.25, presumably due to the weakened microwave irradiation and insufficient heat release. The spectrum analysis of supplied power using the fast Fourier transform (FFT) algorithm indicates that the supplied power characteristics of endothermic reactions are different from those of exothermic reactions. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.