A four-channel serpentine flow-field proton exchange membrane fuel cell model is built based on the conservation equations and reaction mechanisms using COMSOL Multiphysics. This paper analysis the impacts of the mass transport on the fault state. The cathode pressure-drop increases exponentially in the concentration polarization region, demonstrating its sensitivity under PEMFC fault state. When the voltage drops from open circuit voltage to 0. 3V, the average molar concentration increases from 0.97789 mol $/m^{3}$ to 8.3663 mol $/m^{3}$ of water, reduces from 5.4324 mol $/m^{3}$ to 0.8979 mol $/m^{3}$ of oxygen, and decreases from25.815 mol $/m^{3}$ to 18.951mol/m 3 of hydrogen. The results indicates that water flooding and oxygen starvation are the primary causes of performance degradation and pressure-drop rises.