By means of the TM satellite remote sensing data (1999 to 2004, 2008, and 2009) and temperature, precipitation meteorological data (1999 to 2009),an analysis is conducted by means of ARCGIS, ARCVIEW, ENVI saftware. It is concluded that the area of Lake Tangra Yumco presented an enlarging trend significantly in nearly 11 years. The area of Lake Tangra Yumco increased to 85201 km2 in 2009 from 83697 km2 in 1999, and the most obvious enlargement is found in the southeastern part of the lake. The rising temperature, which resulted in the melting of the glaciers and permanent snow cover around the basin, and the increasing precipitation of the lake are the major causes.