The aim of the present study was to compare the antioxidant system of two algae harvested from the Tunisian north costal region. Also we searched a potential resource of new antioxidant compounds, which can be used in health field or for food quality determination. Two Mediterranean, green and vigour algae: Codium bursa (Olivi) C. Agardh and Caulerpa racemosa var. cylindracea (Sonder) Verlaque, Huisman and Boudouresque were chosen for this purpose. The two species belonging to the Ulvaceae, grew in Sidi Raies a coastal region in Tunisia. Activities of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT) and peroxidase (APX)]; carotenoïds as well as chlorophylls (a and b) and protein soluble contents were determined. Our result indicated that there are an important accumulation of carotenoids and chlorophylls; furthermore, the activities of antioxidant enzymes SOD, CAT and APX showed a positive correlation with antioxidant content in the two algae, revealing that they were resistant to the growth medium conditions. But in the other hand, all their antioxidants products and enzymatic activities were higher in Codium bursa than in Caulerpa racemosa means that Codium bursa had higher resistance to the medium thus it could be a good model for culture and production of healthy, useful, such as carotenoids.