Abstract: The utilization of hydrogen is being elevated to an unprecedentedly important role with the aims of green and low-carbon transformation of global energy as well as carbon peaking and carbon neutrality goals. With the growing application of PEM Fuel Cell System(PEM FCS), much higher environmental adaptability performance and longer durability are needed. As the altitude increases, the air is rarefied, oxygen partial pressure is also lower. This kind of environment will limit the performance of PEM FCS and reduce its durability. In this paper, the qualitative analysis of high-altitude effects on the performance of PEM FCS' subsystem, components and parts was carried out. Meanwhile, the corresponding solutions were proposed. Thus, it provides an important basis for the design and component selection of the PEM FCS.