Lakes on the Tibetan Plateau are profoundly impacted by climate change. As the primary producers in lake ecosystems, phytoplankton are highly sensitive to environmental changes, making them key indicators for understanding how lake ecosystems on the Tibetan Plateau respond to climate change. From July 2019 to September 2021, we conducted an extensive study involving the collection, identification, and quantification of phytoplankton samples from 72 open water areas across lakes on the Tibetan Plateau. Our investigation revealed a total of 8 phyla and 91 genera of phytoplankton. The phytoplankton density in the lakes varied significantly, ranging from 1.01 μg/L to 8742.24 μg/L, with the majority of lakes exhibiting a density within the 100-1000 μg/L. The phytoplankton-predominant lake types in the region were Bacillariophyta and Chlorophyta, with Bacillariophyta organisms constituting over 50% in 35 lakes, and Chlorophyta organisms exceeding 50% in 18 lakes. Noteworthy the predominant phytoplankton species in lakes of the Tibetan Plateau included Chlorella, Oocystis, Navicula, and Cyclotella. The richness indices of lake phytoplankton were characterized by species, ranging from 1 genus to 25 genera, with an average value of 8.60 genera. The evenness index exhibited in a range of 0.08-0.93, with a mean of 0.55. Similarly, the Simpson index varied from 0 to 0.87, with the average of 0.53. The Shannon-Wiener index displayed a range of 0 to 2.39, with an average of 1.16. Using the Mantel test and RDA analysis, it was confirmed that salinity and conductivity were the primary drivers of differences in phytoplankton community structure, while pH and temperature were the main factors influencing the variations in phytoplankton biomass of the Tibetan Plateau. The findings of this study enhance the understanding of lake phytoplankton on the Tibetan Plateau, providing valuable insights on how lake ecosystems in the region respond to climate change and human activities.