The invention relates to a leakage rate calculating and monitoring method and system.The method includes the steps that preset test data in a real-time information inquiry system is synchronized to a leakage rate calculating database in real time, wherein the preset test data comprises calculating data for calculating leakage rates of a pressurized water reactor power plant in hydrostatic tests in different pressure environments; the calculating data needed for calculating the leakage rates is called from the leakage rate calculating database, and the leakage rates of the pressurized water reactor power plant in the hydrostatic tests in the different pressure environments are calculated according to the called calculating data.According to the technical scheme, the preset test data is synchronized to the leakage rate calculating database in real time, the calculating data needed for calculating the leakage rates is called to calculate the leakage rates, leakage faults can be found in time, and operating parameters of test equipment can be adjusted in time.