Phytobenthos is the community of vegetable organisms, water quality indicators which inhabits the bottom layers of the water basins: fine sediments, rocks, banks, wood or other submerged objects located on the substrate. They are the basic components of many trophic chains in aquatic ecosystems. The communities are attached to the substrate; their characteristics are affected by numerous abiotic and biotic factors: hydrological regime, type of substrate, light, water chemistry, temperature, other biotic communities. Algae present responses to pollution sources due to their indigenous origin. Phytobenthos algae can also be used to assess the status and ecological potential of lentic water bodies, natural and artificial. Phytobenthos samples from submerged supports were collected for analysis by scraping (blade, spoon and spatula) or by washing. Samples can be taken from the surface of fine or hard sediments in which case they can be washed up directly, or collected with the spoon, spatula, syringe (type Janet). If the sample is analyzed quickly in 24 hours, it should be fixed with 40% formalin or alcohol 1:3. For the determination of diatoms samples are prepared in pleurax fixed with a solution of butanol. Water quality saprobic index is determined according to the method Pantle and Buck (1955). For a wider research of water quality in lake Beleu and to study the influence of human activities occurring on the lake and ecological expedition "Beleu - 2014"was organized in November. Analyses were also conducted to reveal full information regarding the influence of both natural and biotic factors on the biocoenosis. During the expedition 5 samples of phytobenthos in 5 monitoring points were collected. In order to fill up the gaps for phytobenthos set of data, samples from different places on the lake were collected during the field survey, which provide an ampler information in comparison with the annual programme of monitoring which contains only one monitoring section. The obtained results allow making the following conclusions: analysis of phytobenthos samples taken from Beleu Lake indicates the abundance of algae from Bacilariophyta and Chlorophyta, and in smaller number, algae from Euglenophyta and Cyanophyta. Diatom algae prevailed both in number of species and in abundance. After analysis of the samples collected predominance of diatom species characteristic to saprobic zone were observed: Rhopalodia gibba – oligomesosaprobic; Cymbella affinis, Fragilaria capucina, Nitzschia dissipata, Amphora ovalis – oligobetamesosaprobic; Melosira varians, Surirella ovata, Synedra ulna, Nitzschia sigmoidea, Navicula lanceolata, Cocconeis pediculus, Gyrosigma acuminatum, Pinnularia viridis – betamesosaprobic, Cymatopleura solea, Caloneis amphisbaena – beta-alfamesosaprobic, Navicula cuspidata, Nitzschia palea, N. acicularis, N. angustata, Navicula cryptochehala, N. pygmaea – alfamesosaprobic. Also there were frequently found the following Chlorophyta algae: oligo-beta – Spirogyra porticales, Rhizoclonium hieroglyphicum, beta – Scenedesmus quadricauda, S. acuminatus, Cladophora fracta and alpha – Ulothrix zonata-. Number of taxa in samples varied from 13 species identified in Girla Manolescu up to the 41 at Sibirica monitoring point. Saprobic index ranged from 2.11 (Sibirica) and 2.34 (Girla Manolescu - bridge). The water quality dynamic varied depending on sector and the human pollution degree. The most polluted sector is Girla Manolescu (bridge) where the water quality corresponds to the III-rd class and is considered "moderately polluted". But in general, the water quality of Beleu Lake according to phytobenthos can be atributed to the II-nd quality class ("good").