The progresses in the studies in the recent years of NAM/AO （Northern Hemisphere Anuular Mode / Arctic Oscillation) are reviewed, with the emphases on the influences of the NAM/AO on weather and climate, the physical mechanisms of NAM/AO，the waveflow interaction theory, and the baroclinic Rossby wave and quasistationary planetary wave activities on the NAM/AO’s three regional activity centers. During recent years, many studies show that tropospheric fluctuations of NAM/AO are associated with baroclinic waves, while fluctuations are associated with the quasistationary planetary waves in the stratosphere. It is found that the regions where baroclinic wave activities are frequent are the Pacific and Atlantic in the Northern Hemisphere, and the peak value areas are manifested as storm tracks. Besides, the wave breaking is the trigger of NAM/AO events in North Atlantic. On the other hand, the stratospheric zonal winds modify the upwardpropagation of the troposphereoriginated planetary waves, and then these waves refract, reflect and break, which thereby create fluctuations in the strength of the polar vortex in winter. The planetary waves link the NAM/AO’s three regional activity centers: the horizontal propagation and dispersion of quasistationary waves are crucial for the Pacific storm tracks, and the latitudinal position of the Pacific storm track plays an important role for determining the phase of NAO; the propagation of quasistationary planetary waves into the stratosphere over high latitudes can alter the intensity of the polar vortex.