Lake change, as a mirror of climate change, has sensitive responses to climate change. The authors extracted information of all lakes in Inner Mongolia and Xinjiang from Landsat of the 1970s, the 1990s, around 2000 and 2010 based on RS and GIS and developed the spatial database of lakes. On the one hand, through a statistic analysis of lake spatial data using ArcGIS, the authors detected the dynamic changes of lakes in Inner Mongolia and Xinjiang from the 1970s to 2010 or so in the light of time and space. On the other hand, some representative lakes whose area is larger than 5 km~2 were selected to analyze the dynamic changes one by one, and division of these lakes into expansion area and atrophy area was made according to the dynamic changes. From the 1970s to the 1990s, lakes in south Inner Mongolia and west Xinjiang were shrunk whereas lakes in other places of the study region tended to expand. From the 1990s to 2000, lakes in south Inner Mongolia were shrunk whereas lakes in north Inner Mongolia and Xinjiang were expanded. From 2000 to 2010, lakes in east Inner Mongolia and west Xinjiang were shrunk whereas other lakes were expanded. Under the background of the global climate warming, the authors analyzed annual mean temperature, annual rainfall and annual evaporation data of forty meteorological stations, and reached some conclusions based on the data obtained:in the past forty years, annual mean temperature in Inner Mongolia and Xinjiang kept rising;annual rainfall in Inner Mongolia had kept growing before 2000 but decreased suddenly after 2000, and annual rainfall in most part of Xinjiang tended to increase;annual evaporation in Inner Mongolia and Xinjiang tended to decrease. Dynamic changes of lakes in Inner Mongolia-Xinjiang region were consistent with the variation tendency of climate. With the Boston Lake of Xinjiang as an example, the authors finally analyzed the factors responsible for the lake changes, i.e., climatic environment and human activity.