Unicellular green alga Dunaliella and salt tolerant plants suitable model system to study the kinds of stresses. Some species of high salinity, high light and lack of ability to produce large amounts of beta carotene factors are high, hence the microalgae Dunaliella in biotechnology research is important. Beta-carotene is a precursor of vitamin A and has strong antioxidant activity. The activity of free radicals produced in the body cleared and destroyed . The objectives of this study, separation and purification of microalgae Dunaliella from the Persian Gulf, isolated microalgae molecular identification and optimization of physicochemical parameters were evaluated . isolation and purification using culture continuousand salinity changes in the culture medium (30, 40 and 50) and the culture and dilution in liquid medium, purification was performed. Based on morphological characteristics and morphology of three species of Dunaliella were identified. To confirm the identify of morphology, molecular identification 1% CTAB method was used. polymerase chain reaction of gene amplification 18srRNA, Pair of universal primers 18s and specific primers (P73 and P47) with the bonding temperature was 55 ° C. Based on the sequencing results obtained and BALST three species of Dunaliella parva, Dunaliella pesedosalina and Dunaliella salina were identified. To optimize the physicochemical characteristics of the four indices salt concentrations (15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65 and 70%), pH (7, 7/5, 8 and 8 / 5), sodium nitrate (0, 1, 5, 10, 15 and 20 mM) and sodium bicarbonate (0, 50, 100, 150 and 200 mM) during the period of growth in three times for two species of Dunaliella parva, Dunaliella pesedosalina was done. Medium matches the best physicochemical parameters obtained in previous experiments and f/2 were prepared and the rate of growth was measured and the amount of beta-carotene. The growth rate and the amount of beta-carotene in significant differences in the tr