A field emission cathode structure includes an insulating substrate, a number of strip cathode electrodes, a number of insulators, a number of strip gate electrodes, a number of electron emission units, and a number of fixing layers. The number of insulators is located among and spaced apart from the number of strip cathode electrodes. The field emission cathode structure further satisfies the following conditions: D1≦D2/10, wherein, D1 is defined as a width of each of the number of insulators, and D2 is defined as a distance between centerlines of each two adjacent field emission units of the number of field emission units.