Marine algal is one of marine resources which has a potent antioxidant activity. This research aims to explore two species of Indonesia's marine algal, Eucheuma cottonii and Eucheuma spinosum, as a natural antioxidant. In this work, Seaweed Eucheuma Sp. originated from Labuan Aji beach, Nusa Tenggara Barat, Indonesia, were extracted into two different polarity of organic solvents, that is, semipolar solvent of ethyl acetate and polar solvent of ethanol. The extracts were used for phytochemical test and analyzed by Thin Layer Chromatography (TLC). Afterwards, antioxidant activity evaluation of ethyl acetate, and ethanol extracts Eucheuma cottonii and Eucheuma spinosum were conducted by DPPH method. Phytochemical analysis of those two Eucheuma Sp. extracts are positive for a secondary metabolite of flavonoid, triterpenoid, alkaloid and tannin. TLC analysis revealed that the extracts contain one until four chemical components. Among Four concentrated extracts of Eucheuma Sp., the best antioxidant activity has shown by polar ethanolic extract of Eucheuma cottonii with IC
value of 35.51ppm, suggesting that ethanol extract of Eucheuma Sp. is potential to be developed as a promising naturally obtained antioxidant.