The invention discloses a method and system for determining measurement stability of voltage of a measuring winding of a power supply type voltage transformer. The method comprises the following steps: when the measuring winding is in a no-load state and a full-load state respectively, monitoring voltage of the measuring winding after error compensation of power winding voltage of the power supplytype voltage transformer under different power loads, and primary side voltage of the power supply type voltage transformer under different power loads; acquiring a measurement error of the voltage of the measuring winding and the primary side voltage under each power load; and comparing the measurement error under each power load with a preset error threshold, so as to determine the measurementstability of the voltage of the measuring winding of the power supply type voltage transformer. According to the method for determining the measurement stability of the voltage of the measuring winding of the power supply type voltage transformer provided by the invention, the measurement error of the voltage measuring winding of the power supply type voltage transformer under different power loads when the measuring winding is in the no-load state and the full-load state can be measured, so that the measurement stability of the voltage of the measuring winding of the power supply type voltagetransformer is determined, and data support is provided for the on-site operation of high-capacity power supply transformers.