Field emission cold cathode electron source has a wide range of application prospects in many vacuum electronic devices. Carbon materials suitable for cold cathode materials include carbon nanotubes, carbon microtubes and carbon fibers. Field emission characteristics based on single graphite fiber were studied. Single graphite fiber (MGF) was synthesized by chemical vapor deposition (CVD) in a tubular furnace with methane as carbon source. The DC field emission test was carried out in a vacuum chamber by building a diode structure. A single graphite fiber with a length of 3.426 mm and a spherical radius of 11.26 μm was selected and fixed on the copper plate as the cathode, and a conductive ITO glass was used as the anode. The opening field strength of MGF is confirmed to be 0.477 5 V/μm. Furthermore, the electromagnetic field was analyzed based on the simulation software of ANSYS. The effective emission area of MGF under different voltages was calculated. The results show that when the voltage is 5.36 kV, the maximum emission area of MGF is 796.226 μm2 and the average emission current density can reach 46.069 A/cm2 in the experimental voltage range. The monomer graphite fiber has good field emission characteristics.