Abstract: The phenomenon and causes of drought in southwestern China under the background of global warming are studied by the coupled model FGOALS and compared with the observed station data and the NCEP reanalysis dataset.Analyses show that during the drought the subtropical high in the western Pacific is weaker and displaces eastward than in the normal year and the atmospheric circulation in the mid-high latitudes is smoother with a weaker activity of cold air.These lead to a weaker northward water vapor transportation to the western edge of the subtropical high.The water vapor fluxes in the low-mid levels appears anomalous divergences compared to the wet years.Thus,the weakening of convection over the Tibetan Plateau in the upper reach of southwestern China is a main cause of the reduction of precipitation and high temperature over the southwestern China.The geopotential height simulated by FGOALS is lower than that in the NCEP reanalysis in the mid-high levels and the biases increase upward.As simulated by FGOALS,the water vapor transportation locates to the south compared with the observation and the convection is displaced westward.