The flow field design and coolant properties of a proton exchange membrane fuel cell(PEMFC) stack for vehicles were studied to evaluate the effect of gas speed and pressure on the bipolar plate's flow field.The assembly of the PEMFC stack is also analyzed including locating,matching,and selecting of assemblies and the sealing.The PEMFC stack was tested in steady state and transient experiments.The results show that the PEMFC stack has excellent performance with enough hydrogen flow so that the stack has normal output during transients which is important for vehicular applications.