A severe drought occurred in Southwest China in spring of 2010 and it resulted in serious economic loss and social problems, especially in Yunnan Province. The distribution and dynamic change of drought are revealed using the TVDI (Temperature Vegetation Dryness Index) based on EOS/MODIS data. Several different types of data, including weather situation, V-3θ diagram, ncep reanalysis data, water content of atmosphere are used to analyze the characteristics of the temperature and humidity on land, atmospheric circulation and energy structure. The results show this severe drought is the result of together with the atmospheric circulation, the air energy structure and evaporating by the land high temperature: 1) Since January 2010, most areas of Yunnan Province experienced the drought, except the Nujiang River Basin in the northwest part of Yunnan Province. 2) The TVDI are sensitive to both the land surface temperature and water content of atmosphere, which lead to the conclusion that it is reasonable to take both of them into consideration when monitoring and evaluating drought. 3) During this severe drought, the vapor content of atmosphere was lower than the multi-year average, as a result of the maintenance of dry northwest wind in the southwest of China. 4) The solar radiation made the temperature of surface increased significantly, leading the relative humidity was low throughout the whole troposphere. These results can provide some theoretical bases and useful references for the forecast and monitoring of the severe drought.