SVoltage boosting is a difficult problem when it comes to the on-site calibration of 550kV long distance GIS voltage transformer in giant hydroelectric power station. The choice, combination and control of power frequency resonant power supply are key technique to solve the problem of boosting. This paper introduced a power frequency resonant power supply system which is used in the on-site calibration of 550kV long distance GIS voltage transformer. The resonant reactor of the power supply consists of small fixed reactor and controllable reactor. The power supply can realize the power frequency voltage resonant boosting of550kV GIS primary circuit in a capacitance range of 1000pF to 40000pF and can be used as a boosting power supply for on-site voltage transformer calibration and other experiments. The application results show that the power supply system has properties of flexible, light-weight, combination control, strong adaptability and high practical value.