According to the World Health Organization, traditional or alternative medicine or even herbal medicine is known to be the sum of all the knowledges, skills and experiences of a crop, harnessed to prevent, treat and diagnose different diseases using the different plants present in nature and the environment of a region or country. Rhaponticum acaule belonging to the Asteraceae family, it is a North African plant, common throughout northern Algeria. The roots and leaves of Rhaponticum acaule are the main species used in the traditional pharmacopoeia against diseases stomach, tuberculosis, and rheumatism. The main objectives of our work are: the phytochemical study of the hexanoic extract of Rhaponticum acaule and the evaluation of the antioxidant activity of this extract. The hexanoic extract of the roots of Rhaponticum acaule was obtained by simple extraction using hexane, the plant extract was screened for the presence of alkaloids, tannins, terpenoids, saponins, flavonoids, and quinolins and the antioxidant activity was evaluated by two methods using the free radical 2,2-diphényl 1-picrylhydrazyle and the Ferric Reducing Ability of Plasma. The qualitative phytochemical analysis of this plant shows that it is composed mainly by terpenoids. The result of the evaluation of the antioxidant activity reveals that the hexanoic extract is endowed with a very powerful antioxidant activity characterized by inhibitory concentrations of 50% of the free radical 2,2-diphényl 1-picrylhydrazyle (12,5 µg/ml) better than the ascorbic acid (23,5 µg/ml). In fact, these new results could lead to powerful approaches for the research and development of new antioxidant compounds.