Background: Marine algae, especially brown species, produce a wide range of metabolites with various biological activities. Objective: Since marine algae are rich source of dietary fibers, minerals, proteins, vitamins and phenolic components with antioxidant effect, in addition to the rule of oxidative stress in pathogenesis of chronic diseases, the aim of this study was to investigate possible antioxidant activity and total phenolic contents of three brown algae species (Sargassum swartzii, Cystoseira myrica, Colpomenia sinuosa) collected from Asaloye-Niband marine protected area of the Persian Gulf. Methods: Antioxidant activity and total phenolic contents of partitional fractions of n-Hexane, Chlorofrom (CHCL3), Ethylacetate (EtOAc) and Methanolic extract of the samples were studied. Total phenolic contents was measured using Folin-Ciocalteu method while ferric reducing antioxidant power (FRAP) assay were used to study their antioxidant activity. Results: MeOH -H2O and chloroform fractions of Sargassum swartzii were found to have the highest antioxidant activity as 73.92  12.3, 55.32 ± 4.8 mmol FeII per 100 g dried plant and total phenolic contents, 12.0  0.5, 11.05 ± 0.64 mg gallic acid equivalents per 100 g dried plant respectively. Discussion: There was a significant Correlation (R2=0.999) between the antioxidant activity and total phenolic contents of MeOH-H2O fractions obtained from total extracts of these algae. It is recommended that these algae could be potential sources of natural antioxidants.