Hydrogen and oxygen permeation of Nafion 211 membranes (25 μm thickness) was evaluated under variable temperatures, relative humidity (RH) and gas difference pressure between the anode and cathode (P).The results indicate that the gas permeation rate in the Nafion 211 membrane increases almost as exponential form with the rise of temperatures and as linear form with the rise of pressures.However, the effect of RH on the hydrogen permeation seems to be more complicated.At constant temperature the permeability goes through a minimum at intermediate relative humidity (approximately 40% RH).Temperature and pressure have more conspicuous effects on the super-thin membrane permeability compared with the RH.