The role of plankton as natural food affects the potential of fish in the waters. The structure of the plankton community in the Aneuk Laot Lake can provide an overview of the stability of these waters. This study aims to determine the plankton biomass and the structure of the plankton community of Aneuk Laot Lake Sabang. This research was conducted in September 2019 in the waters of Aneuk Laot Lake. Determination of observation stations using the stratified random sampling method, identification of plankton using the census method and analysis of chlorophyll-a using the Trichomatic method. The results showed that the plankton composition consisted of 27 phytoplankton and 4 zooplankton genera which were divided into Bacillarophyceae (36%), Chlorophyceae (19%), Cyanophyceae (16%), Zygnematophyceae (10%), Dinophyceae (3%), Euglenophyceae (3%) and Crustacean class (13%). The abundance of plankton was 21,333 ind/l, the most abundant type is Navicula sp. Diversity index value (2.97) is category high, eveness index (0.87) and low dominance index (0.07). Chlorophyll-a values ranged from 2.84 to 4.84 mg/l including the medium nutrient category. Aneuk Laot Lake has a high level of community stability with trophic status of mesotrophic-eutrophic.