This study exhibits a novel and simple process to test durability of the gas diffusion backing (GDB) with a microporous layer (MPL) and simulates operating a proton-exchange membrane fuel cell (PEMFC) that produces liquid water. One of the major concerns of the gas diffusion layer (GDL) inside a PEMFC is durability. From the analysis of morphology, resistance, and Gurley porosity, the characteristics of each GDL are compared. In long time water washing, the in-plane resistance of the GDL reduces from 29 to 23 m Omega/cm(2) over 200 h. The GDL shows a higher performance (1227 mA/cm(2) at 0.3 V) in long time water washing (200 h) than GDB at a low voltage region (1093 mA/cm(2) at 0.3 V). The high GDL degradation rate causes the migration of the site of MPL during water washing. The inside MPL is weaker than the outward on performance in a PEMFC, but it keeps performance better than GDB.