Abstract: Partially synthesized homoharringtonine, one of the four cephalotaxine ester alkaloids exhibiting antitumor activity consists of two stereoisomers. A novel method of separation and determination of the two epimers by reverse phase ion-paired HPLC with ODS column was described. Sodium heptanesulfonate was used as the counter ion and methanol-water (1:1.26) containing NH₄OAc and tetrahydrofuran at pH 3.5 as mobile phase. The effect of pH, temperature and composition of the mobile phase on the chromatographic process was investigated. Gelsemine was chosen as internal standard and quantitative analysis by peak height has been sucessfully established. The standard curve is linear in the range of 0"～8 μg of homoharringtonine. The method is simple and rapid.