To understand steam reforming of methanol (SRM) reaction pathways over the surfaces of various metal modified molybdenum carbides, the reaction intermediate species generated during the SRM reaction are investigated by using a temperature programmed surface reaction (TPSR) approach, in which a mass spectroscopy is applied to detect the produced species on-line. It is found that the reaction temperature affects the formation of different intermediate species over different catalysts. At the temperature lower than 180 degrees C, SRM reaction proceeds over Cu modified molybdenum carbide surface through formic acid (HCOOH) intermediate pathway, but at the temperature over 180 degrees C, the reactions over pure beta-Mo2C, Ni, Cu and Pt modified molybdenum carbide surfaces proceed through methyl-formate (HCOOCH3) intermediate pathway. It is expected that these findings can help us to understand the mechanism on SRM reaction over molybdenum carbide based catalysts. (C) 2016 Elsevier B.V. All rights reserved.