Abstract: Abstract: On the Qinghai-Tibet Plateau there are three superlarge lakes, the Qinghai Lake, Nam Co and Siling Co, and eleven large lakes, the Zhari Nam Co, Tangra Yumco, Ayakkum Lake, Bangong Co, Har Lake, Ngoring Lake, Yamzho Yumco, Gyaring Lake, Chibuzhang Co, Ulan Ul Lake and the Ngangla Ringco. The authors studied the changes of these major lakes in the past 25 years, based on interpretations of the MSS images obtained during the middle 1970s and ETM+ images obtained in the late 1990s or at the beginning of the 21st century. The study shows that: the areas of the Har Lake and Ngoring Lake have remained relatively stable; the areas of the Qinghai Lake, Zhari Nam Co, Tangra Yumco, Ayakkum Lake, Gyaring Lake, Ulan Ul Lake and Ngangla Ringco have been reduced to varying degrees, of which the areas of the Qinghai Lake and Ulan Ul Lake have decreased most sharply by 60.60 km2 and 59.80 km2 respectively; the areas of the Nam Co, Siling Co and Bangong Co have increased more or less, of which the area of the Siling Co has increased most sharply by 140.52 km2. The analysis on the changes in areas of major lakes has provided new materials for the study of the lake evolution, climatic change and environmental variation on the Qinghai-Tibet plateau.