Abstract: Based on the statistical analyses, the vortices arising in summer (JJA) from 1991 to 2004 are divided into two categories，that is, the moving and stagnant ones. Based on the comparison of composite circulation in these two kinds of vortex cases, the three-dimensional structure of the background general circulation and the influence of the moisture condition on the development and movement of the southwest vortex are studied. The results show that in the moving vortex cases, the atmosphere in the middle and upper troposphere around middle latitudes over the eastern part of the Tibetan Plateau is much colder than that in the stagnant vortex cases caused by the cold air invading. The colder air leads to the lower geopotential height, on the south side of which, the stronger westerly winds prevail from the tropopause to 850 hPa, with the maximum on 200 hPa. The great gradient of the west wind velocity difference at the upper levels enhances the divergence and upflows over the eastern part of the Sichuan Basin. And the stronger westerly winds at the lower levels result in the stronger moisture transport in the southwestern part of the Sichuan Basin. It benefits the eastward movement of the southwest vortex.