Abstract: A kind of combined quantum chemistry method(DFT/AM 1) is employed to calculate O—H bond dissociation enthalpies(BDEs) and ionization potentials(IPs) of fifteen flavonoids,by which their antioxidative activities are evaluated,and the structure-antioxidative activity relationship of some of these compounds is discussed.It was found that in non-polar solvents compounds 3,7 and 8 have the highest activity,and compounds 11,15 have the lowest activity to scavenge free radicals.And in polar solvents compounds 3,4 and 5 have the highest activity to scavenge free radicals.It can be concluded that in polar and non-polar solvents compound 3(3,7,3′,4′-Tetrahydroxyflavone)has the highest activity to scavenge free radicals,suggesting that it is a potential efficient drug for anti-tumor,anti-bacteria and anti-virus.