Abstract: Based on the 500hPa geopotential height data over the Northern Hemisphere of May, June and July 1972- 1982, the atmospheric energy density of wave number domain, the angular momentum meridional flux, and the conversion rate of eddy Kinetic energy to zonal kinetic energy are computed and their spectral diagrams are constructed. By investigating into those diagrams, some significant changes in the energetic feature of the general circulation during the seasonal transition from spring to summer can be found which are believed to have close relationship with the onset of the well - known Met - yu weather event over China in early summer.