This　paper　aims　at　investigating　the　effect　of　the　rough　gas　diffusion　layer　(GDL)　on　liquid　water　transport　behaviors　in　gas　channels　(GCs)　employing　the　volume　of　fluid　(VOF)　in　the　commercial　CFD　package,　FLUENT　6.　3.　26.　It　is　found　that　the　liquid　water　on　the　hydrophilic　rough　GDL　tends　to　spread　along　the　corner　and　presents　as　a　water　film　with　the　concave　surface,　with　many　holes　in　the　GDL　covered　by　the　liquid　water,　whereas　the　liquid　water　on　hydrophobic　rough　GDL　presents　as　the　water　droplet　which　covers　less　holes　and　can　be　easily　drained　out　of　the　GC,　indicating　that　a　hydrophobic　GDL　surface　is　desirable　in　PEMFCs.　Simulations　then　focus　on　investigating　the　effects　of　the　rough　hydrophobic　GDL　on　the　liquid　water　transport　behaviors　in　GCs.　The　simulation　results　show　that　the　droplet　is　inclined　to　form　the　Cassie　droplet　on　the　rough　GDL　surface.　The　water　droplet　is　easier　to　be　drained　out　of　the　GC　with　the　rough　GDL　surface.　The　water　coverage　ratio　for　the　cases　with　the　rough　GDL　surfaces　is　lower　than　that　with　the　smooth　GDL　surface.　The　higher　the　roughness　is,　the　less　the　GDL　surface　is　covered　by　water.　The　pressure　drop　in　the　GCs　increases　with　the　increase　of　GDL　surface　roughness.　©　All　Rights　Reserved.