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Sargassum oligocystum and Nizamudiinia zanardinii are the most abundant algae distributed in the north of Persian Gulf and Oman Sea. In this study after sampling and preparation of S. oligocystum by Chroform-Etanol (3-1) solvent and N. zanardinii by methanol has been extract. Separation and purification of the compounds was carried out using thin layer, general and inverse column chromatography, Cephadex and high-performance liquid chromatography (HPLC ).. Structural elucidation of the constituents was based on the data obtained from HNMR, 13C-NMR, HSQC, HMBC, DEPT and Cephadex LH-20. The steroids compounds separated from above algae were identified as 22-dehydrocholesterol (1) cholesterol (2) fucosterol (3) 29-hydroperoxystigmasta-5,24(28)-dien-3β-ol (4) 24-hydroperoxy-24- vinylcholesterol (5) a mixture of 24(S)-hydroxy-24-vinylcholesterol (6) and 24(R)-hydroxy-24- vinylcholesterol (7) and ostreasterol (8) based on their spectral data and from comparison with those previously reported in the literature.