Beta-carotene being a carotenoid is known as the most famous natural pigment. Microalgae are considered as the most important sources of beta-carotene synthesis. Due to the high sterilization cost of a pure culture, in this study, and for the first time, growth, levels of beta-carotene and chlorophyll in Caspian Sea microalgae (under nutrient deficiencies' stress) have been assessed, and compared with the pure microalgae of Dunaliella Salina.The initial vs final concentrations of beta-carotene under nitrogen starvation (after 188 hours) amounted 7.5, 14.8 vs 7.0, 3.5 mol Beta-Carotene/g Protein for pure vs mixed cultures, respectively. Under nitrogen starvation the final protein concentration of microalgae Dunaliella Salina increased from 341.8 to 950.1 mg/L. However, for Caspian Sea mixed microalgae the concentration was raised from 357.1 to 1010.0 mg/L. The operating conditions were the same for both samples as follows: pH=7.5, temperature 24-26oC and stirring at 160 rpm. This study demonstrates that the accumulated Beta-carotene in Caspian Sea microalgae was comparable to the obtained one from pure microalgae of Dunaliella Salina. Therefore, mixed microalgae culture can be used for Beta-carotene production which is preferable and more economical than sterile system needing processes. Consequently, the possibility of process industrialization would also be enhanced.