A new structure of field electron emitter was proposed to reduce the dispersion of electron beam emitted. In this structure the gate electrode is placed at the center and surrounded by cathode electrode, and then the gate electrode not only plays extracting electrons from cathode but also focusing the electrons emitted. The distribution of the electric field and the electron trajectory of the emitter were investigated and the optimum parameters including geometrical and electrical parameters about the electron emitter are obtained. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3389136]