effect of silymarin as natural antioxidants and antimicrobial activity was main target of the present study. Physicochemical properties of the sunflower oil, and its fatty acid fractionated using GLC method were determined. The ratio between Σ PUFA / ΣSFA, MUFA / ΣPUFA and ΣUSFA / ΣSFA was 4.23, 0.49 and 6.29 respectively. Antioxidant activities of the silymarin were evaluated using Rancimat test at 100 ºC and calculated at 25ºC using the temperature coefficient of 2.2 and the DPPH• radical scavenging method. The addition of the different concentrations of silymarin to sunflower oil (100 to 500ppm) led to clear increment in relative stability % and increasing index of sunflower oil (137.589 to 144.889% and 37.563 to 44.880) compared with BHT (107.329% and 7.317) at100ºC respectively. The DPPH• radical scavenging activities (%) were increased with increasing silymarin concentration from 100 to 450 ppm from70.27±0.19% to 86.77± 0.0.2% respectively. Meanwhile 500ppm of silymarin slightly lowered its value to 83.78±0.15% than that of 300 to 450ppm (86.77±0.02%) still higher scavenging activity (%) compared with BHT (72.78±0.25%) at 200ppm. Antimicrobial activities of each concentration of silymarin were measured and the data indicated that different concentrations of silymarin had exhibited antimicrobial activities against gram-positive bacteria (Bacillus subtilis ATCC 33221,Bacillus cereus ATCC 33018,Bacillus cereus NRRLB 3711and Staphylococcus aureus ATCC 20231), gram negative bacteria (Escherichia coli ATCC69337, Escherichiacoli 0157 and Pseudomonas aeruginosa, ATCC 9027 ) , molds (Aspergillus niger NRRL326 , Aspergillus flavus MERCN 101, Aspergillus parasiticus and Penicillium sp.) and yeast (Geotericum candidum NRRLY552 ). No antimicrobial activity of silymarin concentrations was noticed against either Saccharomyces cerevisiae NRRLY 3034 or Candida lipolytica NRRLY1095. The antimicrobial activity of silymarin was found to be increased in parallel with increasing the concentrations against all tested microorganisms strains. It could be concluded that, the silymarin can be used as natural antioxidants and antimicrobial activity in food industry.