Flow field is a critical component of proton exchange membrane fuel cell (PEMFC), since it directly influences the transfer of reactants, products and heat that in turn influences cell performance. To improve PEMFC performance, various flow field designs are proposed and some of them have been utilized in commercial fuel cell stacks. Although previous studies have investigated the effects of flow fields on reactant/product transport and distribution, few studies evaluate their effects on thermal management especially in fuel cell stacks which is of great significance in practical use. Therefore, in this study, 5-cell stacks with commercialized flow field designs, including Ballard-like straight flow field, Honda-like waved flow field and Toyota-like 3D mesh flow field, were simulated by CFD to investigate their thermal-management performance evaluated by stack average temperature, temperature uniformity and maximum temperature difference. It is demonstrated that Toyota's 3D mesh flow field is able to enhance oxygen supply and liquid water removal obviously, but surprisingly, it results in the worst temperature uniformity and the highest maximum temperature difference which pose a challenge on the stack reliability.