A field emission electron source (10) includes a conductive base (12), a carbon nanotube (14), and a modifying layer (16). The conductive base includes a top (122). One end (142) of the carbon nanotube is electrically connected with the top of the conductive base. The other end (144) of the carbon nanotube extends outwardly away from the top of the conductive base. The modifying layer (16) is uniformly distributed and coated onto at least the surface of the other end of the carbon nanotube. The work function of the modifying layer is lower than that of the carbon nanotube.