Surface microstructure plays a key role in tuning the catalytic performance of Pt base nanomaterials as the oxygen reduction reaction (ORR) catalysts in fuel cell. In this work, carbon supported chemically ordered Pt3Co and PtCo nanoparticles (NPs) with stable Pt shell were synthesized using a polyol reduction process and followed by annealing. The structural characterizations show that the assynthesized Pt3Co/C-700 and PtCo/C-700 catalysts have small particle sizes (similar to 5 nm) and are composed of ordered core and Pt-rich shell. The electrochemical tests show that the ORR catalytic activities of Pt3Co/C-700 and PtCo/C-700 are 0.4978 A mg(-1) Pt and 0.4092 A mg(Pt)(-1), which are higher than that (0.1646 A mg(Pt)(-1)) of the commercial Pt/C catalyst. The stability tests show that the Pt shell of the ordered catalysts was electrochemically stable and the chemically ordered structure was well remained after 5000 potential cycles. The mass activity decreases for the Pt3Co/C-700 (8.60%) and PtCo/C-700 (38.65%) catalysts are less than that (55.22%) of the commercial Pt/C catalyst, displaying superior catalytic stability. The improved catalytic performance of the ordered catalysts was attributed to the synergistic effect of compact arrangement of surface Pt atoms and ordered core. Here we propose a strategy for optimization design of Pt-base catalysts with both high catalytic activity and stability for the ORR. (C) 2017 Published by Elsevier Ltd.