The performance of proton exchange membrane fuel cells (PEMFCs) is affected by impurities, and airborne NO2 is a potential factor in the degradation of the performance and durability of PEMFCs. Herein, the effect of 50 ppb ∼ 5 ppm NO2 on PEMFC was investigated by the poisoning strategy of increasing concentration gradient, and the effect of NO2 on the local current density distribution was explored in both galvanostatic and potentiostatic states. The results showed that 2 ppm NO2 caused a significant voltage decay accompanied by an increase in activation impedance and mass transfer impedance. NO2 was decomposed into oxygen atoms and adsorbed NO on the Pt surface, occupying active sites, impeding oxygen reduction reaction, and further hindering mass transfer. Polarization curve results showed more pronounced voltage decay at high current densities. Polarization curve testing and clean air purging were effective in restoring the poisoned PEMFC. Moreover, it was proved that the poisoning effect is more severe in the inlet region, especially in potentiostatic state. Hence, it is suggested to operate in galvanostatic state, which has a positive impact on reducing the uneven performance caused by NO2. This study provides a reference for the prevention of PEMFC poisoning and performance recovery after poisoning.