To develop a high performance liquid chromatographic method for the simultaneous determination of quercetin and kaempferol in Polygonum aviculare.The optimized method was achieved for the separation and detection of quercetin and kaempferol using Kromasil C18 column (4.6 mm x 250 mm, 5 microm) as the stationary phase, methanol-0.1% aqueous phosphoric acid solution (65:35) as the mobile phase at a flow rate of 1.0 mL x min(-1), 366 nm as the detection wavelength. The main factors, extraction solvent extraction time, hydrolysis tine, temperature and hydrochloric acid concentration, which influenced the sample extraction and hydrolysis procedure, were intensively explored.Methanol and 65% methanol were chosen as the extracting solvent for the free compounds and for the total compounds, respectively. The optimized hydrolysis procedure was that the sample was hydrolyzed 1.0 h with 4.0 mol x L(-1) hydrochloric acid at 80 degrees C. Quercetin and kaempferol showed good relationship at the range of 0.58-362 mg x L(-1) and 0.51-320 mg x L(-1), respectively. Both of the correlation coefficients of the calibration curves were 0.999 9. The detection limits of quercetin and kaempferol were 0.03 mg x L(-1) and 0.02 mg x L(-1) at a signal-to-noise ratio of 3, respectively. The average recoveries of quercetin and kaempferol were 99.7% and 99.0% with relative standard derivation (RSD) of 1.7% and 3.9%.The results showed that the method is simple, accurate and repeatable and it is suitable for quality control of Polygonum aviculare.