The available indicators of catalysts for oxygen reduction reaction (ORR) activity are typically characterized at high potentials (commonly at 0.9 V), whereas fuel cells generally operate at 0.8V similar to 0.6V in its practical application. In our work, charge-transfer resistance (R-ct) was proposed to evaluate the ORR activity of catalysts for fuel cells at rated voltage. Firstly, the R-ct of MEA with Pt/C catalysts was measured in the range of 0.68V similar to 0.92V. Tafel slopes calculated from R-ct were approximately 80 mV/decade at high potentials, whereas the value increased with the decline of potentials below 0.8 V. It showed that R-ct as the ORR indicator of catalysts has certain rationality preliminarily. Secondly, the R-ct of MEA with PtxCoy/C catalysts was compared with Pt/C catalysts. It was lower than that of Pt/C in the high potential region, indicating that the higher ORR activities than that of Pt/C catalysts in higher potential region. Whereas they tended to be the same in the low potential region, indicating that the same ORR activities in rated potential region. Thirdly, R-ct of MEA with Pt/C catalysts during durability test was monitored. It was interesting that the R-ct increased by nearly 125.6% after 900 hours. (c) The Author(s) 2019. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited.