Abstract: Carbon nanotubes(CNTs) are widely used as cathode materials for electron sources due to their excellent electrical properties and large aspect ratio.Benefiting from the high stability and long lifetime of CNTs, they are favored in electro-vacuum devices with high-voltage electrodes.The application of MEMS(Micro-Electro-Mechanical System) tech-nology in the CNTs electron source facilitates the miniaturization of vacuum components such as mass spectrometry, ionization vacuum gauges, and micro thrusters.In this paper, a CNTs based three-electrode field emission electron source with gas injection and ion transport channels is designed, which can provide electron beam for ion source of MEMS mass spectrometry.Through simulation analysis and experimental test, the influence law of the gate structure and electric parameters on the field emission performance is studied.In the simulation analysis, the maximum field emission cathode cur-rent is 46.085 μA, and the electron transmittance is 64.28%;in the experimental study, the highest field emission current density is 1.62 A/m², and the electron transmittance is 75.34%.