Limited by the computational efficiency and stability, traditional 3D (three-dimensional) CFD (computational fluid dynamics) simulations of PEMFC (proton exchange membrane fuel cell) are always in singlechannel scale, which neglect the realistic flow field structures in commercial PEMFC. In this study, a large-scale PEMFC (109.93 cm(2)), which is a repeated unit in commercial stacks and includes realistic anode and cathode flow fields, is investigated in detail utilizing a comprehensive 3D multi-phase model. In particular, the Eulerian-Eulerian model is chosen for the solution of gas and liquid two-phase flow in flow fields and the surface tension, wall adhesion, drag force and gravity are all taken into consideration. The gas concentration and liquid water amount in each channel of flow field are studied to test the influence of flow field. Moreover, it is proved that increasing operating pressure is helpful to improve PEMFC performance by increasing the reactant gas concentration and membrane water content significantly. Besides, counter-flow arrangement of hydrogen and air facilitates uniform distribution of membrane content and electrochemical reaction. And in this case, the coolant flow direction designed to be the same with that of air is beneficial to PEMFC performance. (C) 2018 Elsevier Ltd. All rights reserved.