The nondivergent barotropic vorticity equation on a Hemisphere is solved by the spectral method (T42) with the real drought circulation data to calculate the forced field of the drought circulation pattern under circumstances with and without the topographic forcing. The formation and maintenance of drought circulation pattern under the effect of the forced field and the collapsing process after the dissipation of the forced field are numerically simulated. The results show that the forced field plays an important role in the processes of formation, maintenance and collapse of the drought circulation pattern, and the Tibetan Plateau’s topographic forcing makes the drought circulation’s formation and collapsing faster over its northeast region.