Abstract: This study establishes an integrated electro-thermal model of a PEM electrolyzer, capturing the multiphysical coupling between electrochemical and thermodynamic processes during water electrolysis. A global sensitivity analysis (GSA) is employed to identify the key influencing parameters, thereby enhancing the efficiency of model calibration and improving physical interpretability. The grey wolf optimizer (GWO) is applied to jointly optimize the dominant factors in both the voltage and temperature sub-models. The results demonstrate that the proposed model effectively characterizes the electro-thermal behavior of the PEM electrolyzer under various operating conditions, providing a solid theoretical foundation for subsequent system-level optimization and energy efficiency evaluation.