This study focused on phytoplankton structure, a biotic limiting factors in phytoplankton bloom at the 5 stations  between 2013 and 2014 in the Chitgar Lake. This study identified 35 phytoplankton taxa comprised of Diatoms (12 genus), Chlorophyta (15 genus), Cyanophyta (4 genus), dinoflagellates (2 genus) and chrysophytes (1 genus) in the lake. The finding showed, the Diatom abundance dominate (average of 2060000 ± 230000 cells.l^-1) in the Chitgar Lake. The annual average phytoplankton abundance was calculated as 2550000± 304000, with the maximum value recorded in February 2013 (4400000 ± 450000 cell. l^-1). The PCA analysis displayed, the Diatoms Cyclotella sp., Achnanthes sp. and Chrysophta Dinobryon sp. were dominated in the study period. Based on the CCA analyses, total nitrogen and water temperature were the significant parameters to increase Cyanophyta and Dinoflagellata abundance in the Chitgar Lake. In overall, the lowest phytoplankton abundance recorded in the Chitgar Lake as compared with other lakes which is an Oligotrophic with the latest trophy state lake.