There are a great deal of euthermes which distribute widely in Yunnan Province.The euthermes can be divided into four types: chliarothermes,euthermes,acrothermes and hyperthermes. Cyanophytes in these euthermes are different in the types of population,and also their flora are similar to those of in the tropical and subtropical areas such as Xizang and Sichuan Provinces of China and India etc.In this paper, 89 species of thermal cyanophytes in Yunnan were studied. These species belong to 21 gerera,7 families, 4 orders and 3 classes. The structures of their population,  flora  and  distribution  as  well as the relationship between species diversity and the environmental factors were analysed and discussed.