Abstract: Loose parts monitoring system（LPMS） is a basic security tool for monitoring loose parts in primary loop. One of the problems of detecting loose parts is false alarm. In order to identify false alarm events, this paper analyzed the alarm data and working condition and got the conclusion: if the event happened during the process of reactor coolant pump start and stop; event caused by lightning storm; event caused by the switch of fan on top of the reactor vessel; event happened during the temperature and pressure increasing of the reactor, these alarms are false alarms. The solution for these kinds of typical false alarms is given.