A HPLC method for the determination of triptolide and epitriptolide was established. A Hypersil ODS column was used, with the mobile phase of methanol water(45∶55). The detection wavelength was 220 nm. The calibration curves of triptolide( r =0.9998) and epitriptolide( r =0.9996) were linear. The average recoveries were 100.2%( RSD 0.36%) and 99.6%( RSD 1.03%), respectively. The accuracies were 0.73% and 0.52%, respectively.