Abstract: The objective of this study is to investigate the potential reduction of polarization in proton exchange membrane fuel cells (PEMFCs) through the design optimization of flow channel. The impact of structural parameters and surface properties of the bipolar plate flow channels on the PEMFC performance is thoroughly examined on a commercial scale PEMFC with an active area of 203.49 cm2. The fabrication of bipolar plate flow channels with different structural and wetting properties is achieved using a novel ultrafast laser technique and a conventional milling method. Single cell stack is assembled and subjected to polarization curve tests. The findings indicate that decreasing the width of the flow channels generally improves the performance of commercial-scale PEMFCs. The minimum allowable channel width is dependent on the length of the flow channels. Interestingly, flow channels with higher hydrophilicity and surface adhesion do not necessarily lead to poorer water removal capability, which may be attributed to the formation of a thin water film on superhydrophilic channel surfaces. This research provides valuable insights into the design of optimal flow fields for commercial-scale PEMFCs.