The phytoplankton of 12 salt lakes in Naqu region, Tibet had been investigated during April to May in 2009. A total of 58 species of phytoplankton were identified, belonging to 39 genera of 6 phyla. Bacillariophyta (34 species) was dominant in species richness by 58.62 percentage, followed by Cyanophyta (11 species) and Chlorophyta (8 species). Navicula sp., Nitzschia sp., Lyngbya limnetica, Oocystis parva were the main dominant species. The average density and biomass of phytoplankton were 9.70×104 cells/L and 0.162 8 mg/L, respectively. This paper also discusses the phytoplankton community characteristics of Tibet salt lakes, and the relationship between floristic composition characteristics of phytoplankton and environmental factors, especially the salinity. The results show that the correlationship between phytoplankton species, density, biomass and salinity were not significant(P＞0.05). In salt lakes, the salinity is an important limiting factor in determining the structure of phytoplankton community, and it is controlled by numerous ecological factors.