Exhausting CO₂ in time and effective transferring of methanol solution to the diffusion layer have important influence on the performance of the liquid feed direct methanol fuel cell (direct methanol fuel cell, DMFC). VOF has been used to study the evolution of CO₂ gas which leaked from the parallel channel, including growth, deformation, detachment and motion of the bubble. A three-dimensional model of channel has been established to study the effect of wettability on bubble evolution in channel. The software FLUENT was used to simulate and analyze the diffusion layer wall surface of hydrophilic (35^o), neutral (90^o),weak hydrophobic (115^o) and strong hydrophobic (125^o)。The analysis results show that the bubble is jointly by the pressure difference between the two phases, and surface tension effect as well. The surface of the weak hydrophobic diffusion layer is conducive to the process of bubble separation and bubble coalescence, that is, it showed bubble discharging is more stable compared with the hydrophilic surface, while smaller bubble volume and shorter escaping time compared with the strong hydrophobic surface.