Response surface methodology (RSM) with Box-Behnken model for multicriteria optimization of antioxidant phlorotannin extraction (TPC) from brown algae Sargassum baccularia was used in the research. The investigated conditions were 24-60°C extraction temperature (X1), 16 - 42h extraction time (X2) and 10-50 (v/w solvent-to-material ratio (X3). Methanol was used for extraction. The result showed that objective functions such as minimum carbohydrate (Yl), maximum phlorotannin (Y2), maximum total antioxidant (Y3) and maximum reducing power (Y4) correlate with 0,057mg carbohydrate, 0,1 56mg phlorotannin, 0,867mg acid ascorbic and 0, 995mg FeSO4
19 dry material (DM). The optimal conditions for objective functions were 47°C and extraction time of 36 hour with 43:1 (v/w) a solvent-to-material ratio. This brown algae was collected on 5/2010 at Lo river, Nha Trang city, Khanh Hoa province.