Abstract: Particle identification system by time of flight technique in three body reac-tion spectrometer is reconstructed at IAE cyclotron facility. A automatic frequencytrimming system is developed to reduce the instability of the accelerating phase inthe cyclotron. Besides single peak in time of flight spectrum of monoenergoticparticles from specific two body reaction is used to monitor the shift of time offlight spectra from the three body reaction and to correct it accordingly. Asa result the time resolution of the spectrometer routinely obtained is less than3ns.