Abstract: The antioxidant model (DPPH radical, hydroxyl radical, superoxide anion radical, reducing power, and ABTS⁺ radical) and principal component analysis were used to evaluate the antioxidant abilities of various fractions (normal butyl alcohol, ethyl acetate, chloroform fraction and water) from Sedum aizoon L. using ascorbic acid and hydroxyanisole as control. In the determination of antioxidant activity indicators in vitro, the antioxidant ability of various extraction phases increased with the increase of the concentration of flavonoids. Moreover, the free radical scavenging activities for ABTS⁺ radical of them was the strongest, which was equivalent to that of Vit C and reached 99.72%±0.10%. The hydroxyl radical, superoxide anion radical and ABTS⁺ radical scavenging activity, FRAP value and reducing power of ethyl acetate extract were significantly stronger than those of other solvent extracts. The DPPH radical scavenging rate of normal butyl alcohol extract was higher than those of other solvent extracts. The antioxidant capacity of ethyl acetate extract was strongest according to the principal component analysis results. The results of infrared spectroscopy and color reaction demonstrated the ethyl acetate layer and normal butyl alcohol layer perhaps was flavonols. These data suggested that the flavonoids in Sedum aizoon L. have strong antioxidant activity and can be used as health food raw materials.