The invention relates to an inversion device of high-voltage generator, which is arranged in an inversion chamber integrally mounted in a cabinet of a high-voltage generator, and which comprises one or a plurality of inversion units. Each inversion unit is an assembled modular integral structure formed by mounting a MOS transistor, a radiating fin and an adapter panel of inversion plate on an inversion plate. Each adapter panel of inversion plate is provided with a plurality of twin electric connection holes, which is mounted on a bottom plate of the inversion chamber through an adaptor bracket. The inversion device of high-voltage generator is convenient to assemble, easy to manufacture, and effective to increase work efficiency and reduce false assembly. The cooling mode is so reasonable that a cooling fan is controlled by a temperature switch and needs no long-term operation, and the rear portion of the inversion chamber is provided with a back-up plate with air vent to correspond to an air vent and an air channel arranged on a side door of the cabinet of the high-voltage generator, thereby enlarging draught area, quickening heat dissipation of the inversion chamber, and reducing outward radio-frequency radiation caused by the inversion chamber.