The invention discloses an automatic control method of a high-power direct-current standard resistance box. The method includes: outputting a control signal of a stepper motor by a controller; and carrying out forward/reverse rotation by the stepper motor according to the control signal, and driving a knob driving mechanism. The knob driving mechanism is composed of a knob locking device and a driving shaft. The driving shaft is connected with the stepper motor module, and rotates as the stepper motor rotates. The knob locking device is used to fix the driving shaft on a resistance value setting knob of the high-power direct-current standard resistance box, and enables the resistance value setting knob to rotate accordingly when the driving shaft rotates. Therefore, automatic control of aresistance value of the resistance box is realized, the difficult technical problems that when a high-power direct-current standard resistance box is used for calibration, computer automatic-control is difficult to realize, and display values of resistance boxes are difficult to automatically input are solved on the premise of not changing an electrical structure and measurement performance of thehigh-power direct-current standard resistance box, interference of an automatic control part with an original resistance measurement circuit is eliminated at the same time, and measurement accuracy is enabled to be ensured.