The invention relates to a nuclear power station pressure pipeline leakage acoustic emission monitoring method and a monitoring system thereof. The monitoring method comprises the following steps that: a pressure pipeline leakage test piece is prepared; the defects of initiation, cracks, expansion and even through leakage of a nuclear power station pipeline are simulated; a leakage acoustic emission calibration test is taken; and the pipeline through crack leakage of the high-temperature and high-pressure environment of a nuclear power station is simulated. The monitoring system adopts a standardized and modularized design based on a PCI extensions for instrumentation (PXI) bus, so that the system overhaul and the part replacement are convenient. According to the invention, the data recording of leakage events and the database management of monitoring results can be carried out, and the leakage positions and the dynamic changes of the leakage rate thereof can be comprehensively reflected.