Abstract: A coincident technique is a normal technique which has extensive applications in fields of nuclear physics，basic physical parameter measurements and material science. The influence of recoil electron on the coincident count rate is discussed. Count rate of real coincident from gamma-gamma coincidence changes with threshold in conditions of high and low background. The experimental result suggests that spectrum from recoil electron could increase count rate of real coincidence，the count rate of total coincidence would be affected by the count from background in conditions of high and low background. The effect from the background could be deduced by data correction.

Key words: coincident measurement, NaI detector, recoil electron