Abstract: Taking Inonotus obliquus as test material,the single factor(solid-liquid ratio,extraction temperature,concentration of ethanol,extraction time)on extraction rate of flavonoids from Inonotus obliquus were studied,and the extraction methods were optimized by orthogonal test. Antioxidant activity of samples was determined from three aspects,using the method of FRAP,DPPH·,ABTS⁺·. The results showed that the effect of flavone content from Inonotus obliquus were in order extraction temperature>concentration of ethanol>extraction time>solid-liquid ratio. The optimum extraction conditions were as follows:The extraction temperature was 75℃,the concentration of ethanol was 60%,the extraction time was 2.0 h,the ratio of material to liquid was 1:25 g/mL,the content of flavonoids was 53.25 mg/mL,the extraction rate was 10.66%. When the concentration of flavonoids of Inonotus obliquus was 200 μg/mL,the total antioxidant capacity of that was equivalent to 464.53 μmol/L FeSO₄. The EC₅₀ of clearance on DPPH· was 36.44 μg/mL,the EC₅₀ of clearance on ABTS⁺· was 299.89 μg/mL. The results showed that the clearance rate of flavonoids from Inonotus obliquus for DPPH· and ABTS⁺· was close to V_C,which proved strong antioxidant activity and potential natural antioxidants used in the future.