Based on Landsat TM/ETM+/OLI remote sensing images in the period from 2000 to 2014, the vectorized boundary of 111 lakes with areas greater than 10 km² in northwest China were obtained by artificial visual interpretation technology and the causes of lake variations were analyzed. Several conclusions can be drawn from the present study:(1) From 2000 to 2014, the lakes in northwest China have expanded, with lake areas increasing from 1.58×10⁴ km² to 1.74×10⁴ km². (2) The lakes showed an overall expansion trend; however, several regional differences were noted and, thus, as shown in the figure 4, the study area could be divided into five sub-regions based on changes in the area of the lakes. The lakes in northern Xinjiang Uygur Autonomous Region and southern Qinghai Province remained stable. The lakes showing an expanding trend were widely distributed in the Inner Mongolia-Xin Jiang Lake Zone and the Tibetan Plateau Lake Zone. This region from west to east included the Tarim Basin, northern piedmont of Kunlun Mountains, Altun Mountains, Hoh Xil, Qaidam Basin, southern piedmont of Qilian Mountains, and the northern Three-River source region. The lakes that were shrinking were primarily located in two regions that consisted of the central northern Xinjiang including Junggar Basin and the Turpan Depression, and the northern Karakorum Mountains. (3) The reasons behind the lake area changes in the different regions differed owing to the complex environment in the study area. For the region where the lakes were expanding, an increase in precipitation and melt water from glaciers and frozen soil due to climate warming were the dominant factors behind the changes. The state of glacier mass balance and human activities played an important role in the region where the lakes were shrinking in area, while in the region where the lakes remained stable, the topographic characteristics of the lakes such as intensive hydraulic connection between lakes and rivers were the main factors behind the observed results.