Abstract: With the concept of wave packet and using WKB method, the all-round characteristics of the Rossby wave packet under the background of the basic current and the topography are obtained, and the equation and condition for the development of the wave pocket are got as well. Applying the condition obtained to the background basic current of southwest and southeast jet, the conception of the wave packet breaking and the wave passage branching is proposed, i. e. according to the location of the wave packet with respect to the jet and the condition satisfied by the stationary wave packet, its trough (ridge) line has to be deformed, bending, breaking and bifurcating, the wave passage hence bifur-Gates correspondingly. As to the SW jet, one bifurcated wave packet propagates toward high latitude, and upward penetrates into the stratosphere, the other one propagates toward the low latitude, whereas it propagates a far less distance than the former, and upward only attains the tropopause. By means of the feature of the wave passage bifurcation of the Rossby wave packet in the SW jet, the EU type teleconnections suggested by Wallace et al. are investigated.