The invention discloses a nuclear power station primary circuit foreign matter monitoring system and a nuclear power station primary circuit foreign matter monitoring method. The system comprises a loose component and vibration monitoring device (1), a reactor core filter screen pressure difference monitoring device (2) and a processing device (3). In the nuclear power station primary circuit foreign matter monitoring system, the loose component and vibration monitoring device is used for acquiring monitoring signals of all devices in a primary circuit when the primary circuit triggers preset conditions which are set according to starting conditions of a primary pump; when the primary circuit triggers the preset conditions, the reactor core filter screen pressure difference monitoring device is used for acquiring pressure difference signals on two sides of a reactor core filter screen, so that the system starts to conduct foreign matter monitoring in a primary circuit start phase to avoid any foreign matter monitoring blind zones; moreover, the reactor core filter screen pressure difference monitoring device is connected with the processing device, so that the trouble of on-site routing inspection is avoided, and manpower resources in the primary circuit start phase are saved.