Abstract: RP-HPLC was applied to the determination of 3 flavonoid aglycones,including quercetin,kaempferol and isorhamnetin in zanthoxylum bungeanum.The sample solution was separated by using Zorbax Eclipse C18 column (4.6 mm×150 mm,5 μm) as stationary phase and a mixture of methanol and 0.4% (φ) phosphoric acid solution (mixed 1 to 1 by vol.) as mobile phase.The contents of the 3 flavonoid aglycones were determined at the wavelength 360 nm.Linear relationships between values of peak area and mass concentration of quercetin,kaempferol and isorhamnetin were kept in ranges of 2.19-109.6 mg·L-1,2.28-114.0 mg·L-1 and 2.80-140.0 mg·L-1,respectively.Tests for recovery and precision were made by standard addition method.Values of recovery and RSD′s (n=5) found were 95.6% and 2.98% for quercetin,104.4% and 3.97% for kaempferol,103.8% and 4.30% for isorhamnetin,respectively.