In this study, a native microalgae strain with a high capability of DHA production has been isolated and purified from mangrove shores in the Persian Gulf. Morphological and molecular identification based on 18S rRNA gene showed that the isolated strain belongs to Aurantiochytrium genus. In order to optimize the growth of this strain, various environmental factors were examined, including temperature (15, 20, 25, 30 and 35°C), salinity (10, 30 and 50 g L^-1) and different concentrations of nitrogen sources of yeast extract, peptone, meat extract and monosodium glutamate, each of which was tested at the concentration of 10 g L^-1. The findings show that the optimal growth conditions occur at temperatures of 25-30 °C, pH equal to 6 and in the presence of meat extract as the nitrogen source. In these conditions, the cellular biomass weight, fatty acids and DHA amounts obtained were 7.34, 2.25 and 0.4 g L^-1, respectively. These results imply that the new isolated strain of Aurantiochytrium sp. shy it can be suitable for lipid production.