Using FeN 2 -gra as a single-atom catalyst to oxidize toxic CO into non-toxic CO 2 . • Different N and C atom configurations on FeN 2 -Gra have little effect on the thermodynamic stability of the structure and the gas adsorption performance. • The maximum energy barrier required for CO oxidation by FeN 2 -hex through LH mechanism is 0.270 eV, while the RLS of FeN 2 -opp and FeN 2 -pen are 0.673 eV and 0.697 eV, respectively. • The remaining O atom in the process of generating the second CO 2 are very easy to achieve, realizing the recycling of the catalyst. Single-atom catalysts (SACs) can maximize the utilization of metal atoms and reduce manufacturing costs, so they have been extensively studied. This study used density functional theory (DFT) calculations to discuss in detail the CO oxidation reaction (COOR) mechanism on non-noble metal iron and nitrogen atoms co-doped graphene. It was determined that FeN 2 -Gra is a suitable catalyst for the COOR due to its stable configuration, adsorption performance, kinetic analysis, and catalytic activity. The optimal path for FeN 2 -Gra on COOR is the LH mechanism, in which the lowest energy barrier that FeN 2 C 2 -hex needs to cross through the LH mechanism is 0.270 eV. The rate limiting steps (RLS) of FeN 2 C 2 -opp and FeN 2 C 2 -pen along the LH mechanism are 0.673 eV and 0.697 eV, respectively. According to the theoretical analysis, FeN 2 -Gra is a low-cost, high-efficiency catalyst suitable for COOR, which provides new ideas for subsequent experimental guidance and synthesis of ideal catalysts with superior catalytic performance.