This paper focuses on investigating that the influence of O-2, CO2 and H2O on characteristics of autothermal reforming of methane in micro premix chamber on Ni catalysts. In addition, the effect of catalytic wall temperature on autothermal reforming reaction of methane under a certain ratio of CH4/CO2/H2O/O-2 is simulated. The results indicate that appropriately increasing O-2 concentration can increase the conversion efficiency of CH4, so does adding CO2 or H2O. The positive effect of O-2, CO2 and H2O is more pronounced at the higher temperature. The temperature range of 650-750 K is the important transitional region in the reactions of CH4/O-2, CH4/H2O and CH4/CO2. It also gives a guide to the available range of parameters in the high efficiency reforming process of micro-reactor. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.