We developed a three-dimensional multiphysics numerical model of a Proton Exchange Mem-brane Fuel Cell (PEMFC) with a cathode mesh structure to investigate how coolant flow rate and temperature impact its performance. After experimentally validating the model, we compared the performance of the cathode mesh structure PEMFC with that of the traditional straight flow PEMFC. The results indicate that the cathode mesh structure PEMFC has a lower pressure drop and a more index of uniform distribution (IUD), leading to enhanced performance, better temperature distribution, and improved water management of the PEMFC. The investigation of the cooling system's operating parameters revealed that the temperature of the cathode catalyst layer in the PEMFC is the highest, while the temperature of the bipolar plate is the lowest. Of the nine cases that we evaluated, Case 7, with a coolant inlet temperature and flow rate of 303.15 K and 0.07 m s−1, respectively, yielded the highest power density and the lowest average temperature. The IUD of the PEM in Case 5 was 0.608, suggesting that the temperature distribution of the PEM is more uniform when the coolant inlet temperature and flow rate are 323.15 K and 0.05 m s−1, respectively. We have demonstrated through calculations that there is a strong correlation between temperature difference and IUDs. These findings have significant implications for the optimization and application of PEMFCs.