The shorting resistance (SR) of the PEMFC(Proton Exchange Membrane Fuel Cell) polymer membrane is an important indicator of the durability of the membrane. When SR decreases, shorting current (SC) increases, reducing durability and performance. When SR becomes less than about 0.1 kΩ?cm2, shorting occurs, the temperature rises rapidly, and MEA(Membrane Electrode Assembly) is burned to end stack operation. In order to prevent shorting, we need to control the SR, so the conditions affecting the SR were studied. There were differences in the SR measurement methods, and the SR measurement method, which improved the DOE(Department of Energy) and NEDO(New Energy and Industrial Technology Development Organization) method, was presented. It was confirmed that the SR decreases as the relative humidity, temperature and cell compression pressure increase. In the final stage of the accelerated durability evaluation process of the polymer membrane, SR rapidly decreased to less than 0.1 kΩ·cm2, and the hydrogen permeability became higher than 15 mA/cm2. After dismantling the MEA, SEM(Scanning Electron Microscope) analysis showed that a lot of platinum was distributed inside the membrane.