Abstract: OBJECTIVE To establish a ultra-high performance liquid chromatography with mass(UPLC-MS) method for determination of triolein content, and determine triolein content in Coicis Semen from 23 different regions. METHODS Using Waters Quattro Micro with mass, the column was Acquity UPLC BEH C₁₈(2.1 mm×100 mm, 1.7 μm); the mobile phase was made up that A phase contained methanol, acetonitrile and 0.1% formic acid solution with ammonia to pH 3 in the proportion for 19∶19∶2, and B phase was isopropyl alcohol, the proportion of A phase and B phase was 55∶45; column temperature was 45 ℃; the flow rate was 0.3 mL·min^-1. Detection in ESI using positive ionization and multiple reactions monitoring mode(MRM) was applied to determine positive ions m/z 902.8→m/z 603.2. RESULTS The standard curve was Y=4.233×103X+9.172×102(r=0.999 5), the tirolein in linear range of 0.142-25.56 μg·mL^-1 had a good linear relationship; the average recovery was 97.21%, RSD was 1.44%(n=9); and triolein content in Coicis Semen from different regions was different. CONCLUSION The established UPLC-MS method on determination of triolein content in Coicis Semen is sensitive, rapid, accurate, reproducible and can be used for the quality control of Coicis Semen.