Extraction of polyphenols from Inula viscosa (L.) leaves has been studied using water as a green solvent. Optimization of the process was performed using  response surface methodology (RSM) in order to investigate the effects of three operating parameters, temperature,  solid to liquid ratio and stirring speed (ω) in the following ranges : (28-56 ° C), (2-58 g.L^-1) and (60-341 rpm), respectively. The efficiency of extraction was assessed by measuring polyphenols, flavonoids, and anthocyanins contents as well as antiradical activity. The conditions optimizing the yield of polyphenols and antiradical activity were established   (T=50°C, S/L= 3 g.L^-1, ω= 217 rpm). Under these conditions, polyphenols content was estimated to 291 mg GAE .g DW^-1, and   antiradical power was 83%. Purification of the extract obtained under these optimal extraction conditions increased the antiradical activity to 90%. This antiradical activity is medium  (Antiradical efficiency =  10^-3 g DPPH°. (mg AO. min)^-1 ) with antioxidant characteristics (IC50= 5µg.mL^-1, EC50 = 125 mg AO. (g DPPH°)^-1 and TEC50 = 8min) comparable to those of powerful antioxidants. These results are very promising especially as antioxidant phenolic compounds have beneficial effects on health, and can find major applications in food and pharmaceutical products.