Glacier retreating and increasing number and area of glacial lakes are considered as an important evidence which indicates climate change; the increasing area of lakes makes the lake more dangerous. Therefore, study of the change of glacial lakes is of great significance for research of climate change and glacial lake disaster. Based on Landsat TM/ETM+ remote sensing images, using the method of artificial interpretation, three sets of glacial lake data of the Koshi River basin in 1990, 2000 and 2010,were obtained, the area and length change of 199 glacial lakes, which were surviving lakes with area greater than 0.1 km~2, were analyzed, the followings were revealed:1)The total area of glacial lakes with area larger than 0.1 km~2 in the basin was increasing, from 73.59 km~2 in 1990 to 86.12 km~2 in 2010; 2) In the basin, variation of glacial lakes on the southern slopes of the Himalayas was different from that on the northern slopes of the Himalayas, for example, on the northern slopes, the more changed glacial lakes were located in between the elevations of 4 800 m and 5 600 m, while on southern slopes, they were located in between the elevations of 4 300 m and 5 200 m. On the northern slopes, 65% of glacial lakes was expanding, and the main expanded area was located in the contact of lake with glacier terminal; on the southern slopes, 32% of glacial lakes was expanding, and the main expanding was supra-glacial lake expanding; 3)On the average, the change velocity of glacial lake on northern slopes is slightly greater than that on the southern slopes in the basin.