Three green microalgal species ( Chlamydomonas reinhardtii , Dictyochloropsis splendida , Muriella sp.) were cultured under four stress culture conditions (nitrogen concentrations , light intensity , photoperiod , salinity). The aim of the present study is to evaluate the algal growth parameters , antioxidant and anticancer efficiencies of the stressed biomasses. Extraction was performed by hexane , ethyl acetate , methanol and produced 36 extracts (E1-E36 ). Antioxidant activity of the 36 crude extracts were performed by radical DPPH & non-radical KMnO4. E14 of D. splendida cultivated on 3g L nitrogen was the promising crude extract exhibited the greatest antioxidant activity by both methods. Fractioation of E14 was done by silica gel column chromatography produced 11 fractions (F1—F11) . Greater antioxidant activity of F5, F8 occurred compared to antioxidant standards (Ascorbic acid, BHT). High Performance Liquid Chromatography ( HPLC ) analyses of E14 , F5 , F8 were evaluated and 4 ,5 , 6 Phenolic compounds were produced respectively. Anticancer activity of E14, F5 , F8 as well as the mixture of F5+ F8 was determined against three cancer cell lines ( HepG2 , MCF7 & Pc3 ) against MTT assay. The obtained results showed that fractions and mixture of fractions exhibited greater activity and lower IC50 compared to their crude extract E14 .