The Mg adsorption and diffusion behaviors on nitrogen doped (N-doped) Mo2C monolayer have been systematically investigated by the first principles based on density functional theory (DFT). The adsorption energies of Mg on pristine Mo2C and Mo2C1 − xNx (x = 0.0625, 0.125, 0.1875 and 0.25) have been studied. The adsorption energies of Mg on N-doped Mo2C are lower than that of pristine Mo2C. Especially, the adsorption energies of Mg are − 1.639 eV and − 1.625 eV on TC1 and H2 sites for Mo2C0.875N0.125, which have decreased by 16.49% and 18.43%. Furthermore, the Mg diffuses along H3-B-H4 and H-B-H with the barriers of 0.021 eV and 0.028 eV, which indicate that Mo2C0.875N0.125 exhibits fast diffusion properties. Additionally, the partial density of states (PDOS) reveals the interaction between Mg and Mo2C0.875N0.125. The PDOS results indicate that nitrogen doping causes the PDOS peaks transfer to a lower energy level, which is benefit for the bonding between Mg and MoC0.875N0.125. These results suggest that the adsorption and diffusion behaviors of Mg are enhanced by nitrogen doping.