γ irradiated rutin —, catechin — and baicalin — HCOONa aqueous solutions saturated with N,2,O:O,2,=4: 1 were eluted through alumina columns and the ,G, values of hydrogen peroxide generated in the solutions were measured. Different results from former works were obtained and the reasons of the difference were discussed. A precise method was established as follows: hydrogen peroxide should be separated from flavonoids by passing the flavonoids solutions through alumina columns before the measurement and the amount of hydrogen peroxide generated from self—oxidation of the flavonoids should be deducted. The ,G, values of hydrogen peroxide in γ irradiated rutin —, catechin — and baicalin — aqueous solutions saturated with N,2,O:O,2,=4:1 were determined to be 8.3±0.2, 5.6±0.2, and 7.8±0.2, separately.