The invention discloses a flat-plate filament for an X-ray CT tube, belonging to the technical field of medical instruments. The flat filament for an X-ray CT tube includes a flat plate and an emitting structure formed on the flat plate. The emission structure is a four-pin square or circular structure formed by a plurality of through grooves, and the stability of the structure is improved throughthe four-pin structure, and the filament stress deformation caused by the strong centrifugal force generated by the high-speed rotation of the CT machine is avoided. The plate filament prolongs the service life of the filament by optimizing the groove structure and reducing the ignition caused by the pressure difference between the grooves. By reasonably directing the electric current, the influence of the self-generated magnetic field of the flat filament on the electron beam focusing is weakened, and the focal spot quality is ensured.