Cyanobacteria bloom because seriously eutrophication in Dianchi Lake.This paper bases on GF-5 hyperspectral data and uses NDVI to identify the occurrence of cyanobacteria bloom in Dianchi Lake,and classifies the range of NDVI to further compare and to analyze the spatial distribution characteristics and differences of cyanobacteria bloom in Caohai and Waihai.Conclusions are as follows:①From the general quantitative statistical analysis of the NDVI range,we can get the NDVI mean values of Caohai and Waihai are -0.350 and -0.708 respectively,which means the cyanobacteria bloom coverage in Caohai is much more seriously than that in the Waihai.②According to the classification statistics of the NDVI range,we can conclude that Caohai is dominated by the mild cyanobacteria bloom area,which accounts for 73.36 % of the total area of Caohai.The proportion of severe cyanobacteria bloom area was 1.12 %.Waihai is dominated by the area without cyanobacteria bloom,which accounts for 95.42 % of the total area of Waihai.The proportion of moderate and severe cyanobacteria bloom are 0.52 % and 0.11 % respectively.In general,the spatial distribution of cyanobacteria bloom in Dianchi Lake is in the pattern of "north heavy south light",and the coverage density of cyanobacteria bloom is 80.45 %,which indicates that Caohai is more prone to cyanobacteria bloom than Waihai,and the water quality of Caohai is relatively poor.This method can monitor and identify the spatial distribution of cyanobacteria bloom effectively in plateau lakes in real time,it made hyperspectral remote sensing of lake water quality monitoring methods more abundant,and provided scientific basis for promoting the management,development and utilization of water resources in Dianchi Lake.