Caulerpa lentillifera belong to Caulerpa genus which is commonly found in tropical and subtropical water. The biggest constituent of seaweed is polysaccharide that has some biological activities as a potential medicine. Therefore, this research aimed to extract and evaluate the antioxidant activity from Caulerpa lentillifera polysaccharide. The extraction was carried out by using water extraction. First, the sample was added with ethanol and soaked overnight at room temperature. On the following day, the sample was added with aquades and put in a water bath at 75°C for three hours. After that, ethanol was added to precipitate the extract. The crude polysaccharide extract percent yield obtained 4.16 %. The crude extract purified by using a column with DEAE-Sepharose with percent yield obtained 14.8 %. Both crude and pure extracts were characterized by analyzing the total carbohydrate and sulfate by using spectrophotometer, functional group by using FT-IR spectroscopy and sugar component by using HPLC. Antioxidant activity was analyzed by using the FRAP method for both crude and pure extract. Moreover, the polysaccharide crude extract gives higher antioxidant activity than the purified extract.