OBJECTIVE:To establish a HPLC method for the simultaneous determination of quercitrin and isoquercetin in hypericum japonicum thunb.injection.METHODS:Merck Lichrospher RP 18 was used as chromatographic column and the mo-bile phase consisted of acetonitrile-(pH=3.0)buffer phosphate(18∶82)with flow rate at1ml/min,column temperature at25℃and detection wavelength at350nm.RESULTS:The linear range for quercitrin and isoquercetin were0.278?g～4.440?g(r=0.9991)and0.315?g～2.520?g(r=0.9991),respectively.The average recovery were98.60%(RSD=2.23%)and97.79%(RSD=1.74%),respectively.CONCLUSION:This method is accurate,reliable and applicable,and suitable for the quality control of hypericum japonicum thunb.injection.