This application disclosures a method for calibrating filament current data of an X-ray tube. The method includes obtaining a first value of tube current to be calibrated and a value of filament current to be calibrated, the tube current to be calibrated and the filament current to be calibrated corresponding to a first calibration point performing an emission operation based on the first value of the tube current to be calibrated and the value of the filament current to be calibrated determining an actual value of the tube current during the emission operation determining a difference between the actual value of the tube current and the first value of the tube current to be calibrated and calibrating, based on the difference, the first calibration point.
