The electron field emission performance of CNT doped with one nitrogen atom in different atomic layers and adsorbed with H2O molecules of different numbers was investigated through the first-principles calculations. The results show that the structure of the systems investigated is stable. The margin of the density of states (DOS) shifting towards low energy position increases with the applied electric field and the number of water molecules, and the HOMO/LUMO gap decreases with these parameters. The analysis of adsorption energy, DOS/LDOS, HOMO/LUMO and their gap indicates that N3CNT+βH2O system is more propitious to the electron′s field emission than other systems.