Halophilic, unicellular species of Dunaliella with the lack of a rigid cell wall are the main source of producing natural carotenoid of betacarotene for pharmaceutical industry, aquaculture and animal feed. For these reasons, large-scale production of Dunaliella has received great attention. In this study, continuous cultivation of Dunaliella salina is evaluated in helical photobioreactor at 25 ?C and initial pH of 7.5. For this purpose, sodium chloride medium (1.5 M) and a helical photobioreactor equipped with a cell retention system (CRS) composed of cellulose acetate hollow fiber membranes (CA HFMs) is used. Exposure program is set at 16 h lightness and 8 h darkness with the light intensity of 150 . CA HFMs are produced via dry/wet spinning using CA/(acetoneformamide: 50-50) solution with CA solution of 20 wt.%. The produced CA HFMs are characterized with respect to surface and interior morphologies, tensile strength, hydrophilicity, overall porosity, mean and maximum pore size and pure water permeability. Using the produced CA HFMs with mean pore size of 124 nm and overall porosity of 78/9±2%, the rejection of the Dunaliella salina microalgae is demonstrated to be as high as ~94.9%. Additionally, the produced CA HFMs exhibit a reasonable fouling resistance evaluated using aqueous solution of BSA protein (1000 ppm). The comparison between the performance and productivity of continuous cultivation of microalgae in helical photobioraector without and with CRS showed that the former at dilution rate of 2.05 l/day reaches a productivity of 45.30±3.46 which increases by 200% when CRS is employed as a component of photobioreactor. Continuous cultivation of microalgae in helical photobioreactor without cell retention system in dilution rates of 0.75 and 1.72 l/day showed productivity of 19.03 and 38.20 , respectively. The results vividly demonstrate the superiority of the continuous cultivation composed of CRS over that without CRS. Hence, significantly higher productivity is achieved by the former.