Abstract: RP-HPLC was applied to the determinations of 4 flavoniods including quercetin,kaempferol,luteolin and apigenin in humifuse euphorbia.Method of extraction of sample,and conditions of separation by liquid chromatography were tested and optimized.The ZORBAX SBC18 column (150 mm×4.6 mm,5 μm) was used as stationary phase,and a mixed solution of methanol and phosphoric acid (mixed in the a ratio of 40 to 60 by volume) was used as mobile phase.UV-detection at 360 nm was adopted in the determination.Linear relationships between the values of peak area and mass of 4 flaoniods were obtained in a definite range.The values of recovery found by standard addition method were in the range of 92.70%-99.39%,and values of RSD′s (n=6) were less than 3.5%.