The invention provides a system for monitoring loosening parts of a nuclear reactor and a coolant system, solving the problems of reliability, compatibility, stability and maintenance convenience andcomprising an accelerometer, a charge amplifier, signal conditioning equipment, loosening part detection equipment, alarm processing equipment, sound monitor equipment, data collection equipment, a display, loosening part monitor software and the like. The system adopts a PXI bus technology so as to enable every two modules to be synchronized; a signal conditioning module adopts an FPGA programmable technology; a DSP digital technology is adopted to discriminate a loosening part event; loosening part signal length effective value floating discrimination, time delay, channel recheck combination discrimination, alarm prohibition caused by alarm channel recheck, control rod motion or coolant low pressure, and the like ensure that the system has a strong wrong alarming resistance capacity; the data collection equipment collects data to replace tape records so as to ensure the integrity of event signal records; and event signal waveform display and data storage can carry out display back and secondary analysis on signals.