In order to study the atrophy of the Dongting Lake in the past 100 years, the authors systematically monitored the atrophy of the Dongting Lake based on historical topographic map data, such as the Dongting Lake map in the late Qing Dynasty (AD 1896) which is treasured by the Library of Hunan Province nowadays, aviation photos since 1954, satellite images which were captured by the American KH-8 military satellite in 1967 and other aerospace remote sensing data. The results show that in the past 118 years from 1896 to 2014, the Dongting Lake area has shrunk by 2466.42 km², from 5146.71 km² to 2680.29 km². Now the Dongting Lake area is 47.92% of the lake basin area in 1896. A comparison with the area variation data of the Dongting Lake published by the Water Conservancy Department shows the data obtained by two sources are generally very close, with some differences in some specific areas. After the severe flooding disaster of the Yangtze River in 1998, the State Council explicitly put forward the lake-management policy of "Farmland Conversion to Lake Wetland" so as to stabilize the area of the Dongting Lake. The Dongting Lake is mainly enclosed by artificial levee whose location is irrelevant with sources of water and sands; thus, the operation of "the Three Gorges" since 2003 has had no influence on the area of the Dongting Lake.