In this study, carbon-supported CoPtAg nanoparticles with different atomic ratios have been reduced under CO atmosphere and applied as electrocatalysts for oxygen reduction reaction (ORR). These samples with low Pt loading have comparable ORR activity and stability to Pt/C. An appropriate amount of Ag addition like 5 at % can effectively promote the performance of CoPt owing to the modification of the oxophilicity. Then carbon-supported Co90Pt5Ag5 nanoparticles with different atomic arrangements have been reduced by different agents. The coordination numbers of Pt-Co and Co-Co (CNPt-Co and CNCo-Co) of catalysts are related to their ORR activity and stability, respectively. Co90 sample with Ag and Pt randomly distributing within the Co matrix has high CNCo-Co, which does not have positive effect on the ORR performance. On the other hand, Co90-1 sample with Ag and Pt cores within the Co matrix has the highest CNPt-Co and ORR activity ascribed to the electronic modification effect. However, it losses 32% ORR activity after accelerated durability test of 1000 cycles due to high CNCo-Co. Co90-2 with Pt in the inner core and Ag on the outer shell structure has moderate CNPt-Co, very low CNCo-Co, and un-filled d-states, which not only modify the oxophilicity but also benefit the ORR stability with a decay rate of 21%. We have demonstrated the atomic arrangement-performance relationship of highly stable and low Pt catalysts. (C) 2016 Elsevier Ltd. All rights reserved.