The present application provides an external thermionic cathode distributed x-ray apparatus, including a vacuum box which is sealed at its periphery, where the interior thereof is high vacuum; a plurality of electron transmitting units arranged in a linear array and installed on the side wall of the vacuum box, where each electron transmitting unit is independent to each other; an anode installed in the center inside the vacuum box, where in the direction of length, the anode is parallel to the orientation of the electron transmitting unit, and in the direction of width, the anode has a predetermined angle with respect to the plane of the electron transmitting unit; a power supply and control system having a high voltage power supply and a focusing power supply; and a transmitting control means and a control system.