Algae Division of Phaeophyta (brown algae) is a group of macroalgae that have important benefits for life because they contain bioactive compounds such as antioxidants. This study aims to identify bioactive compounds and analyze the antioxidant activity of algae of the Phaeophyta Division in the genus Sargassum sp. and Padina sp. The methodology in this study included extract preparation by maceration method using 70% ethanol, phytochemical tests using several reagents, phenolic total was carried out quantitatively, and antioxidant activity testing using the 1,1-Diphenyl-2-Pycrihydracyl (DPPH) method. The results showed that Sargassum sp. contains tannins, saponins, alkaloids, steroids, and triterpenoids. Meanwhile, Padina sp. contains only tannins. The yield of Sargassum sp. extract was 0.086% while that of Padina sp. extract was 0.065%. The total phenolic content of the Sargassum sp. extract was 419.133% while that of the Padina sp. extract was 248.467%. Antioxidant activity of Sargassum sp. extracts with IC50 10.93 mg/L and Padina sp. of 10 mg/L. The higher the total phenolic content, the higher the antioxidant activity, in which phenolic compounds are known to play a role in neutralizing free radicals, inhibiting oxidation in body cells, and can prevent cell damage.