This study addresses the electrode polarization issues in iron-chromium redox flow batteries (Fe-Cr RFB) by proposing an in-situ measurement method based on symmetrical cell design. This approach aims to overcome the limitations of existing research, where non-in-situ tests on planar electrodes fail to reflect the true kinetic characteristics of porous electrodes. Using a 0.6 mol/L Fe2?/Fe3? electrolyte and different thicknesses of Nafion membranes (N-212, N-115, N-117), the study quantitatively analyzed ohmic, activation, and concentration polarization through electrochemical impedance spectroscopy (EIS), galvanostatic step testing, and constant-voltage methods. Results show significant differences in polarization behavior among various membrane materials at different current densities, with the N-212 membrane exhibiting the lowest ohmic polarization and optimal electrochemical performance at low current densities. Validation experiments with concentration cells further confirmed the accuracy of the polarization decoupling results. The innovation of this study lies in the in-situ measurement of porous electrode kinetics, providing theoretical insights and data support for optimizing electrode materials and operational conditions in redox flow batteries, and promoting the enhancement and design optimization of flow battery performance.