Abstract: Antioxidant activity of ethanol extracts from Jatropha curcus L. seed shell was determined by evaluating the scavenging activity of superoxide anion radical ( O-2·) , 2, 2- diphenyl-2- picrylhydrazyl radical ( DPPH·) and nitrite ( NO-2) , reducing power and total antioxidant capacity, taking the flavonoids concentration of its ethanol extracts for internal standard and comparing to vitamin C ( VC) and Butylated hydroxytoluene ( BHT) .The results showed that the half inhibitory concentration ( IC50) values of ethanol extracts from Jatropha curcus L.seed shell on O-2·was 0.502 mg /m L, lower than that of VC ( 0.654 mg /m L) .The IC50 values of ethanol extracts on DPPH·and NO-2were 0.185 and 0.494 mg / m L, respectively; both of them were lower than BHT's.When the flavonoids concentration of ethanol extracts in the range of 0.7 to 1.0 mg / m L, its reducing power was equal to that of VC, but stronger than that of BHT. In addition, the total antioxidant power increased with increasing of flavonoids concentration from0.1mg / m L to 1.0mg / m L, which was higher than that of BHT, lower than that of VCat the same concentration though.All of above indicated that ethanol extracts from Jatropha curcus L. seed shell had stronger antioxidant activity.