Abstract: DPPH,ABTS and ferric ion reducing power methods were used to evaluate in vitro antioxidant activity of blackberry seed. The content of polyphenols was measured using the Folin-Ciocalteau method,and the content of total flavones was measured using the Na NO2- Al Cl3 colorimetric method. Correlation between polyphenol and flavone contents and antioxidant capacity was analyzed. The results showed that ethyl acetate extract and n-butanol extract from blackberry seed had DPPH IC50=( 41.93 ±4.05),( 64.75 ±5.89) μg/m L,respectively and ABTS radical scavenging activityIC50=(2.91±0.46),(3.18 ±1.01)μg/m L,respectively,and ferric ion reducing powerTrolox equivalent=(2348.73±2.78),(1262.55±31.58)μmol/g,respectively. Petroleum ether extract had ABTS radical scavenging activityIC50=(21.85 ±0.61)μg/m L and weak ferric ion reducing powerTrolox equivalent=(123.59±10.01)μmol/g. An excellent correlation between ABTS radical scavenging activity of three extracts and the contents of total polyphenols and total flavones were observed(R2=0.6832 and0.2596). Ferric ion reducing power was correlated with the content of total polyphenols(R2=0.990). Blackberry seed had antioxidant activity.