The hot springs of North Pribaykalye were investigated and 41 species and forms of Cyanobacteria, belonging to 3 classes, 5 orders, 8 families and 10 genera were found. The dominant genera were Phormidium, Oscillatoria, Gloeocapsa. Both Seya and Uro springs were the most numerous in cyanobacterial diversity (13 species). At temperature increasing the species diversity decreasing. The greatest species diversity of Cyanobacteria has been observed at temperature range 35–40 оС. The temperature limits for cyanobacteria were 20–69 оС.