The invention relates to the technical field of nuclear power plant primary loop pressurizers, and discloses a nuclear power plant primary loop pressurizer spray valve polarization opening calibrationmethod and system. The method comprises steps: an on-off heater is started; the spray valve is adjusted to a first opening to enable the pressure of the pressurizer to be controlled to drop to the pressure of starting the on-off heater and keep the pressure to be stable; the spray valve is adjusted to a second opening, wherein the second opening is the opening which enables the output power of aproportional heater to reach a preset value and the pressure of the pressurizer to be unchanged; and the second opening is acquired as the polarization opening of the spray valve. The polarization opening of the spray valve acquired by the above calibration method has a smaller fixed value than the traditional spray valve polarization opening, starting of all heaters in the case of polarization operation of the spray valve is not needed, and the method and the system are suitable for polarization operation of the spray valve.