The purpose of research work is establish eleven year variation in the amplitude of third harmonics of daily variation in Cosmic Ray Intensity on sixty quiet days after using neutron monitor data at different latitude Neutron Monitoring Station. It has been observed that in spite of abrupt variation in the 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 also absorbed during the declining phase of earlier solar cycle twenty. Therefore, this enhancement establish the eleven years variation in the amplitude of third harmonics of Cosmic Ray Intensity on quiet days at Equatorial Neutron Monitoring Stations. Further, the amplitude of third harmonics of Cosmic Ray Intensity on quiet days has been observed almost equal during the two consecutive solar maximum activity period of solar cycle twenty one and twenty two supporting eleven years variation in the third harmonics of daily variation at high latitude Neutron Monitoring Station.