First-principle calculations based on dispersion-corrected density functional theory (DFT-D) are carried out to reveal the elementary steps of CO oxidation on Mn-N4 porphyrin-like carbon nanotube (MnN4-CNT). The stability of MnN4-CNT is confirmed by the first-principles molecular dynamics simulation. According to the energetic calculations, CO and O-2 prefer to anchor at the MnN4 site and the adsorption of CO is slightly more favorable than O-2. The three reaction mechanisms of CO oxidation on the MnN4-CNT are explored, namely, Eley-Rideal, Langmuir-Hinshelwood, and a "new" termolecular Eley-Rideal, respectively. It is found that the termolecular Eley-Rideal reaction mechanism is the most favorable one and the energy barrier for the rate-limiting step is merely 0.69 eV. Our results suggest the high catalytic activity of MnN4-CNT for CO oxidation at room temperature. (C) 2017 Elsevier B.V. All rights reserved.