A diagnostic analysis is carried out to investigate the frequency modulation effect of El Nino and La Nina events on atmospheric low-frequency oscillations(LFO)in the mid-high latitudes.The power spectral analysis is performed for the daily Northern 500hPa height field data in the mid-high latitudes from 1950 to 1996.The results show that:(1)the intensity of low-frequency oscillation in winter is stronger than that in summer;(2)main periods of low-frequency oscillations show a shortening/lengthening tendency of low-frequency oscillation period during El Nino/La Nina event.The above results have the significant meaning to the research of the short-term climatic variation.