The two-phase flow problem is one of the most critical challenges for direct methanol fuel cells (DMFC). With carbon dioxide generated in the anode catalyst layer, a bubble that could not be removed from the flow channel would hinder the oxidation reaction. In this paper, bubble generation and flow in a micro-serpentine channel is modeled using a multi-phase three-dimensional Navier-Stokes plus volume of fluid (VOF) method. The bubble generation process, which results from the gas-liquid flow and the effects of surface tension and viscosity, are discussed and validated by a comparison with a serious of experimental results. The results prove that the VOF method is an effective method to simulate flow fields where the bubble flow phenomena exist, such as the two-phase flow fields in DMFCs. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.