Selenium (Se) is a necessary microele-ment for microalgae growth. Moreover, it might be directly act and cause a decrease in primary production in microalgae. Nowadays, there is a great focus on preparations of Se-enriched products. In the current study, the effects of various selenate concentrations on Spirulina evaluated as a primary stage to large-scale production of Se-enriched S. platensis. Zarrouk medium supplemented to investigate the stimulatory/inhibitory effects of selenate on the growth at various concentrations. Biomass dry weight and cell mass measured on OD550. Thereafter, inhibitory and algicidal concentrations were determined. Furthermore, its effects on morphology and changes of some important pigments in response to the metal challenge investigated, too. While the results showed that at 5 and 10 ppm concentrations growth was supported, the dry weight of microalgae decreased at selenate levels above 50 ppm. Besides, the inhibitory and lethal effects of selenate were at 100 ppm and 300 ppm, respectively. In addition, morphological changes observed at this concentration. Additionally, chlorophyll, carotenoid and phycobiliproteins, showed a stimulatory effect at 5-50 ppm, 10 ppm, and 10 ppm, respectively. Moreover, Spirulina uses for foods production because some chemicals are unique compounds. Simple cultivation method and high quality of its protein, and no toxic effects, cause its feasibility for large-scale production.