Abstract: In this paper, the WKB method is used to obtain the nonlinear schrödinger equation satisfied by nonlinear Rossby wave in the rotational atmosphere. It is found that the nonlinear Schrödinger equation has envelope solitary wave solulion under the condition 1≤m≤2,and the phase speed of envelope solitary Rossby wave is related to the square of its amplitude linearly, that is, the largerthe amplitude of envelope solitary Rossby wave, the smaller its propagation speed. Furthermore, the blocking high and cut-off low which are consistent with the observations of blocking in the atmosphere are obtained by calculating envelope solitary Rossby wave, and the blockings persist more than five days, the results demonstrate that the envelope solitary Rossby wave is an possible mechanism about the formation, maintenance and break out of blocking in the atmosphere.