Electrochemical impedance spectroscopy (EIS) offers advantages such as non-destructiveness, wide frequency range, high precision, and applicability in vehicle-mounted systems, making it increasingly popular in the study of proton exchange membrane fuel cells (PEMFCs). However, there is a notable lack of research on impedance measurement and quantitative analysis for high-power fuel cell stacks. This study focuses on high-power fuel cell stacks, conducting EIS measurements under standard operating conditions. The impedance spectra were analyzed using Fast Fourier Transform (FFT) and Total Harmonic Distortion (THD). The results indicate that the DC-DC converter generates harmonic interference at high frequencies. The relaxation time distribution method based on the optimization of characteristic frequency resolution was adopted to optimize the characteristic frequency resolution and regularization parameters, achieving the quantitative identification of the dynamic polarization processes of high - power fuel cell stacks, including the proton transport in the catalyst layer, anode polarization, charge transfer, and oxygen mass transfer processes. This method provides technical support for the quantitative identification of the kinetic polarization processes in high-power fuel cell stacks.