The dynamic performance of proton exchange membrane fuel cell (PEMFC) is critically important, especially for automotive applications. In this study, the dynamic behavior of the local current density distribution inside PEMFC has been investigated experimentally by using the segmented flow field plate and printed circuit board (PCB) method. The effect of different values of air stoichiometry ratios on the dynamic characteristics of local current density has been tested. It has been found that the fluctuation of the local current density increases as the cell voltage is reduced, corresponding to the increase in the average cell current density or cell loading. Increasing the stoichiometry ratio of the cathode supply gas significantly reduces the fluctuations of the current density. The fluctuation is also lower near the flow inlet than near the flow exit. The phenomena observed are closely related to the water and reactant distributions and transports in the cell structure.