An abstract of the study on the characterization of two benthic diatoms isolated from Oran coast is presented. Diatoms (Bacillariophyta) are photosynthetic unicellular organisms with silica cell walls (frustules) that constitute important primary producers in coastal waters. In Algeria few studies have been made on diatoms, but in 2010 Nehar et al. recorded 10 taxa from El-Hammam stream, a thermal water at Mascara, and the estuary of the Cheliff river at Mostaganem. In this study two strains of benthic diatoms were isolated from coastal water in Oran (Algeria) and maintened by resubculturing in controlled light and temperature conditions. Results showed that both biomass and lipid production were higher under lower incident irradiance of 10 μmol photons m-2-s-1 and 25 μmol photons m-2-s-1 and ranges of lipid production varied from 50 to 600 mg L-1. At 60 μmol photons m-2-s-1, Nitzschia sp. produced the maximum concentration of chlorophyll a, 2.88 pg cell-1 whereas Entomoneis alata produced the maximum amount of chlorophyll a under 25 μmol photons m-2-s-1, 2.68 pg cell-1.