The utility model provides a grid
electrode used for a vacuum electronic device, an
electron gun and an X-
ray tube, the grid
electrode comprises a grid
electrode substrate, the grid electrode substrate is a flat sheet, the thickness of the grid electrode substrate is 0.1 mm-3mm, and the
thermal conductivity of the material of the grid electrode substrate is greater than 200W / (m.K); an
electron beam through hole is formed in the gate substrate, the axial direction of the
electron beam through hole is perpendicular to the two surfaces of the gate substrate in the thickness direction, and the electron beam through hole enables the gate substrate to be provided with a through hole part and an entity part except the through hole part; after the electron beam through hole is machined in the gate substrate, an outer wrapping layer is fixedly arranged on the surface of the entity part, the outer wrapping layer is made of a
metal material, and the thickness of the outer wrapping layer is 10 nm to 50 [mu] m. According to the grid electrode, a large amount of heat generated when electron beams bombard the grid electrode can be conducted away, the
high electron passing rate is still achieved under the low kV smaller than 5 kV, and the grid electrode is well suitable for field emission, heat emission, thermal field emission and other various
cathode emission materials.