The investigations of hybrid graphene layers on metal surfaces have attracted widespread attention from both experimental and theoretical scientists, but the catalytic properties of well-known Ni (111)-supported graphene are still unclear. In this work, an unreported C2O2-Langmuir-Hinshelwood (C2O2-LH) mechanism is proposed for CO oxidation (COox) on the Ni (111) supported-graphene surface by density functional theory (DFF) calculations. Our results show that two CO molecules can chemisorb on the Ni (111)-supported graphene merging into the chemisorbed ethylene dione complex (C2O2). Then, the coadsorption of C2O2 and O-2 molecules can form the C2O2 annulus on the Ni (111)-supported graphene. Finally, the C2O2 annulus produces two CO2 molecules through the formation of a ring-like intermediate product (R-L Inter). Specially, we find that this new C2O2-LH mechanism with the co-adsorption of C2O2 and O-2 molecules as the first step achieves much lower energy barrier compared with the prevailing belief of the Eley-Rideal (ER) mechanism with the O-2 activation as the first step. These results suggest that the Ni (111)-supported graphene could be a potential and high-efficient catalyst for COox, which also open fundamental insights into the new reaction mechanism for COox on nanocatalysts. (C) 2017 Elsevier Ltd. All rights reserved.