Southwest China had been suffering from an epic drought in the autumn of 2009. The study area of Tongjin vallage of Dafang county located in the typical fragile karst eco-environment area of Guizhou province was one of the worst hit sites. By meteorological monitoring here, we got plenty of meteorology data about precipitation and temperature, combine with soil erosion situation analysis of this area, setting a drought assessment model. Then, building the drought assessment system based on GIS with its strong managing and analyzing function, study showed the drought situation, grade and relief time of The study area of Tongjin vallage of Dafang county. Meanwhile, proposed the drought countermeasures in fragile karst eco-environment area such as: changing slope to ladder, planting water- holding flora, building cisterns ect.