Antioxidant activities of cholesterol to lipid oxidation in sunflower oil-in-water emulsions( food model systems) stabilized by Tween 20 and soybean phosphatidylcholine liposomes( biological membrane model system) was studied. The effect of ascorbic acid and α-tocopherol on the antioxidant activity of cholesterol in different model systems was investigated. The water soluble azo-compound 2,2'-azobis( 2-amidinopropane) dihydrochloride( AAPH)could be used to generate carbon centered radicals by thermal decomposition for initiating lipids oxidation. Total antioxidant activity( TAA) was measured by ferric thiocyanate assay( FTC) and thiobarbituric acid-reactive substances( TBARS) test. The results showed that cholesterol had antioxidant activities,but was different in different systems. It was clear that cholesterol had the best antioxidant at the concentration of 0. 02 mg /mL in traditional sunflower oil-inwater emulsion. Furthermore,synergistic interactions between the cholesterol and ascorbic acid / α-tocopherol against lipid peroxidation were also investigated. It can be seen that the combination of three different concentrations cholesterol and 0. 0016 mg /mL VE had certain synergistic interactions. The other combination of cholesterol and ascorbic acid /α-tocopherol did not lead to synergistic interactions.