The effect of the compression ratio on the dynamic behavior of liquid water transport in a gas diffusion layer (GDL) is studied both experimentally and numerically. We experimentally study the emergence and growth of liquid droplets in a channel at various compression ratios by adopting a direct visualization device. The results of the experiment show that water breakthrough occurs at the channel for a low compression ratio, whereas it is observed at the channel/rib interface for a high compression ratio. To determine the mechanism of water transport in the GDL, a multiphase lattice Boltzmann method (LBM) is developed for a simplified porous structure of the GDL. The observation of lattice Boltzmann (LB) simulation shows that the compression ratio significantly affects the water transport in the GDL. The results indicate that the lower compression ratio reduces the water saturation in the GDL. The simulation and experimental result are similar. (C) 2015 Elsevier B.V. All rights reserved.