An ultra performance liquid chromatography coupled with tandem mass spectrometric(UPLC-MS/MS) method was established for the simultaneous determination of oleanolic acid(OA) and ursolic acid(UA) in Chinese herbal medicine.The sample was detected by ultra performance liquid chromatography coupled with tandem mass spectrometry(UPLC-MS/MS).The separation of two compounds was achieved on a Waters Acquity UPLC BEH C18 column(50 mm×2.1 mm,1.7 μm) with a mobile phase of 5 mmol/L ammonium acetate in water(ammonium hydroxide adjust pH 9.24) and acetonitrile in gradient elution mode.The detection of the compounds was performed in negative ion mode.The result indicated that the concentration of OA and UA had good linear relationships with peak area in the concentration range of 0.5-50.0 ng/mL,and the correlation coefficients(r2) were 0.999 8 and 0.999 7,respectively.LODs(S/N=3) of the two compounds were 0.006 6 ng/mL and 0.012 8 ng/mL,respectively.LOQs(S/N=10) were 0.002 0 ng/mL and 0.003 8 ng/mL,respectively.The recoveries of OA and UA were 101.1% and 100.8%,with RSDs(n=9) of 1.8% and 0.04%,respectively.The method showed the advantages of simpleness,high accuracy and good reproducibility,and could be used for the detection of OA and UA content in the Chinese herb.