The purpose of this investigation is establish eleven year variation in cosmic ray intensity particularly in third harmonic after using cosmic ray intensity neutron monitor data on sixty quiet days. It has been observed that in spite of abrupt variation in amplitude and phase of third harmonic of cosmic ray intensity, the amplitude of third harmonic is relatively larger during the declining phase of solar cycle twenty one as it is observed during the declining phase of earlier solar cycle twenty. Therefore, this enhancement establishes the eleven year variation in third harmonic of cosmic ray intensity on quiet days at equatorial neutron monitoring stations. Further, no systemic change have been noticed in the amplitude and phase of fourth harmonics of cosmic ray intensity on quiet days, but the amplitude of fourth harmonic during the year 1981 and 1991 having the same value at equatorial neutron monitoring stations.