Based on the NCEP/NCAR reanalysis data， the largescale circulation background and water vapor characteristics of five rainstorm processes in the southern margin of the Taklimakan Desert during May-September (warm season) in 2001-2020 are analyzed and then HYSPLIT （Lagrangian method） method is used to calculate the water vapor trajectory and main path as well as the water vapor contribution of different sources. The results show that the water vapor sources of the rainstorms are mainly the Southwest Asia, central Asia and northern Xinjiang. Water vapor from the source areas passes through northern Pakistan, northwest India, northeast Afghanistan （IPA) and the key areas of southern Xinjiang, respectively into the rainstorm areas from the southwest and north path, the water vapor passing through the key areas of southern Xinjiang contributes a lot to the rainstorm. During the rainstorms on the southern edge of the desert, water vapor in the middle layer of the atmosphere (500 hPa) originates mainly from Southwest Asia, but there is a lot of loss along the way. While in the lower layer (700 hPa), the main contribution of water vapor is from northern Xinjiang, and the loss along the way is small. The water vapor from the northern and southern Xinjiang Basins is mainly transported to 700 hPa from the nearsurface layer. The water vapor from Southwest Asia, the Atlantic Ocean and its coast is transported to the height above 700 hPa. Based on the above features,the three dimensional structure model of water vapor source and path during rainstorm process on the southern edge of the desert is established， and also a more detailed descriptions of the contribution and source of each layer of water vapor are provided.