This study presented a remote sensing/GIS-based method to monitor changes of lakes in the southeast of Qiangtang area, Qinghai-Tibet Plateau. The Landsat TM/ETM+ and CBERS CCD images together with 1:100000 topographic maps were applied to research 22 lakes from the area. Methods changing intensity index and quadrant-azimuth analysis were used to mainly research the urban expansion. The lakes area in recent 30 years were analyzed by changing intensity and spatial differential features. The results showed that the lake area had an expanding trend from year 1975 to 2005, and the total area had enlarged about 1162.19km². Among these lakes, the Selin Co had expanded the latest area with 510.02km² and significant expanding northwards. Meanwhile, the Lake Cuojialun had the highest changing intensity in the area.