Abstract: Spectra analyses on the potential field and the zonally-averaged kinetic energy of meridional motions on the mean monthly 500 mb maps of Northern Hemisphere at latitudes of 60°N and 30°N have been made. The seasonal variations of the amplitudes and phase angles of the first three waves and the differences between high and low latitudes of these quantities, are studied in detail. The results are as follows:1) The chief contributions of the normal potential field are mainly concentrated at the long quasi-stationary waves and show significant seasonal variations. 2) The waves of wave number one have significant differences in the latitudes north or south of about 50°-60°N. The quasi-stationary long waves displace gradually to the west as they approach to the lower latitudes. For example, the quasi-stationary waves at 30°N have been deviated by 1/4 to 1/2 wave lengths to the west from that at 60°N. 3) The primary component of the tonally averaged meridional kinetic energy along 600N is also concentrated in the quasi-stationary waves. The maximum value appears in the waves of wave number n=2-4, the peak value having significant seasoaal varia- tions. The spectra of the tonally-averaged meridional kinetic energy along 30°N caa be roughly classified into three types according to their seasonal variations: a) Winter type: the tonally-averaged meridional kinetic energy along 30°N has the highest maximum value at the quasi-stationary waves near wave number three and the secondary maximum value at the travelling planetary waves (near n=5-8).b) Summer type: the zonally-averaged meridional kinetic energy along 30°N has only one maximum value at the wave of wave number 6-7. c) Transient type: the spectrum of the tonally-averaged meridional kinetic energy along 30°N is rather flat and has no a stationary peak value.