Abstract: Proton Exchange Membrane Water Electrolyzer (PEMWE) is becoming one of the mainstream hydrogen production carriers with the characteristics of high flexibility and high current density.PEMWE internal physical structure is complex,and the flow field of different form had obvious effects on the electrochemical properties.Therefore,based on the coupling theory of multiple physical fields such as heat transfer,mass transfer,and electrochemical kinetics,a 3D model of PEMWE single cell was established to study the influence of flow field structure on PEMWE performance.The fluid velocity,material distribution and polarization curve of four kinds of flow field structures were compared and analyzed.The results show that under the same operating conditions,the material flow velocity and pressure distribution in the groove of cascade flow field PEMWE are more uniform,and the electrochemical reaction is more sufficient,while the electrochemical performance of traditional parallel flow field structure is poor.In addition,under the working condition of 80 ℃ and 0.1 MPa,the polarization voltage of cascade flow field PEMWE is lower,and the polarization voltage of single cell is only 1.686 V when the current density is 2 A/cm2.Therefore,compared with the other methods,the cascade flow structure can effectively improve the PEMWE single cell performance.