In order to clarify the regularity of Dongting Lake blooms, the changing rule of water area and its influencing factors, the MODIS02HKM images were used as the main data sources in the study. The Floating Algae Index (FAI) and a Multi-band Water Index (MBWI) were adopted to identify and extract the water and the scope of algal bloom in Dongting Lake. the temporal and spatial distribution data of water and algal bloom in Dongting Lake in the past 2001~2015 years were analyzed. The research conclusions were as follows:Firstly, the water area of Dongting Lake presented obvious seasonal change in years and a inter-annual reduced trend. The area of water was in order of summer, autumn, spring and winter. In the 2001~2015 year, the average area of water was 2.2times that of the dry season. Secondly, the area shrinkage rate of Dongting Lake in 2001~2015 was-14.574km²/a, and the largest rate was -38.678km²/a in summer. Thirdly, from 2001 to 2015, algal bloom occurred annually in the Dongting Lake area, large-scale algal blooms were usually found in the western part of Dongting Lake. The algal bloom of the West Dongting Lake and the South Dongting Lake were scattered along the river bank. Fourthly, the seasonal and inter-annual seasonal variations of blooms in Dongting Lake were significant. The area of water bloom basically presented normal distribution every year. The minimum value appeared in winter and the maximum value appeared in summer and autumn. The minimum value of algal boom was appeared in winter time, whilst, the maximum value of algal boom appeared in summer and autumn. Its maximum value reached to 681.43km². The largest algal bloom in 2001~2015 years accounted for 16.693% of the total Lake area. The annual average change rate of algal bloom area was -8.657km²/a. Algal blooms showed a trend of area reduction.