A field emission neutralizer is provided. The field emission neutralizer comprises a bottom plate and at least one field emission cathode unit located on the bottom plate. The field emission cathode unit comprises a substrate, a shell located on the substrate, a mesh grid, a shielding layer insulated and spaced from the mesh grid, and at least one cathode emitter located inside the shell, and insulated and spaced from the mesh grid. The cathode emitter comprises two cathode electrode sheets and a graphitized carbon nanotube structure, the graphitized carbon nanotube structure comprises a first portion and a second portion, the first portion is clamped between the two cathode electrode sheets, and the second portion is exposed outside of the two cathode electrode sheets.