|The polymer membrane of proton exchange membrane fuel cell (PEMFC) has a great influence on PEMFC performance and durability. In this study, hydrogen permeability, fluorine emission rate (FER), lifetime, and performance of Nafion membranes with different thicknesses were measured to investigate the effect of thickness of polymer membrane on performance and durability. The relationship between membrane thickness and lifetime was obtained from the relationships between hydrogen permeability and membrane thickness, hydrogen permeability and FER, FER and lifetime. As the membrane became thicker, the hydrogen permeability and FER decreased and the lifetime increased. On the other hand, the performance decreased with increasing membrane resistance. The membrane thickness range satisfying both performance and durability was 25 to 28 μm.