Marine ecosystems have a high diversity of living organisms compared to terrestrial ecosystems and provide abundant resources for human nutrition and health. The aims of this research were to determine total phenolic content, examine antioxidant and photoprotective activity, and characterize brown seaweed Sargassum sp, Turbinaria sp, and Padina sp from North Sulawesi coast component. The total phenolic content was determined using folin ciocalteau method, antioxidant activity was evaluated using total antioxidant, photoprotective was evaluated using Sun Protector Factor (SPF), and characterization of brown seaweed extract using UV-vis and IR Spectrophotometry. The results showed that total phenolic content from Sargassum sp 5,20 mg GAE/g, Turbinaria sp 1,47 GAE/g, and Padina sp 27,45 GAE/g. Total antioxidant of Sargassum sp 0,496 mg AAE/g, Turbinaria sp mg AAE/g, and Padina sp 0,295 mg AAE/g. The SPF value of Padina sp extracted with hexane 20.530, ethyl acetate 28.505, butanol 11.040, ethanol 13.705, and acetone 3.403. Characterisation of brown seaweed extract using spectrophotometer UV-vis consists of phenolic compound, carotenoid, and chlorophyll. FTIR spectra of brown seaweed extract showed that Sargassum sp contain (C-halide), (N-O), (-C=O), (N-H), (C-H) and (OH-) groups, Turbinaria sp (C-halide), (C=C), (N-H), (C-H) and (OH) groups, and Padina sp (C-halide), (C=C), (N-H), (C-H) and (OH-) groups. Brown seaweed possesses antioxidant and photoprotective activity.