Ulva lactuca is widespread green algae. In some regions, it is used in nutrition. Its nutrients include iron, protein, iodine, vitamins (A, B1, and C) and trace elements. Their extracts showed potential antibacterial, hypolipidemic, cardioprotective and chemoprotective activities. The main chemical constituents of Ulva lactuca methanolic crude extract and its fractions were investigated in this study using different phytochemical and chromatographic methods. Biologically guided fractionation of plants or seaweeds extracts is considered the first step in drug discovery. So, the algal crude extract was fractionated then in vitro bioscreened for the determination of diphenylpicrylhydrazyl (DPPH) antioxidant, (Nitric Oxide) NO radical scavenging and anti-inflammatory activities. Results showed that water fraction was the most active fraction. Phenolic content, detected from HPLC, play a role in the antioxidant activity. Finally, it can be concluded that Ulva water fraction is effective candidate to be used in the treatment of oxidative stress and related disorders