Currently, there are only some general concepts about the performance difference between an LT-PEMFC (low temperature proton exchange membrane fuel cell) and an HT-PEMFC (high temperature proton exchange membrane fuel cell), i.e., no literature has been found to conduct direct comparisons between them. In this research, for the first time, according to the same level (low level, medium level or high level) under the same operating condition type (operating temperature or cathode air utilization rate), the tested I-V performance, EIS (electrochemical impedance spectroscopy), LSV (linear sweep voltammetry), and calculated ECSA (electrochemical surface area) are compared between LT-PEMFC and HT-PEMFC. Some mechanisms are further disclosed, for instance, the higher Pt loading in the catalyst layer of an HT-PEMFC and its elevated operating temperature do not result in improved performance, compared to that of the LT-PEMFC. This is attributed to the lower apparent exchange current density in the case of HT-PEMFC.