The utility model discloses a gate-controlled carbon nano-cathode field emission X-ray tube, comprising a radiator, anode components, a vacuum container, cathode components and a wiring tube, wherein, the anode components comprise a transition ring, an anode sealing part, an anode target component, an exit window and an anode cap, and the cathode components comprise a cathode cover, a set screw, a core column cap, a core column, a cathode sealing part, a first insulating ring, a cathode holder, a carbon nano-cathode, a shielding ring, a second insulating ring and a gate. The X-ray tube utilizes the good emission feature of the carbon nano-cathode to use the carbon nano-cathode as one part of the cathode components to be sealed in the vacuum container; an electron beam is pulled out from the surface of the carbon nano-cathode by a gate electric field, and the pulled-out electron beam bombards the anode target at high speed under the excitation of an anode high-voltage electric field and the focusing of the cathode cover. The gate-controlled carbon nano-cathode field emission X-ray tube has the characteristics of high voltage and high penetration, can steadily and continuously work at high voltage, and can output a certain of focal spot and of electron beam of the beam current size.