A high performance liquid chromatography-tandem mass spectrometric(HPLC-MS/MS) method was developed for the simultaneous determination of 31 alkaloids in essential oil cosmetics.A mixture of methanol-H2O(3∶1,by volume) containing 2% formic acid solution was selected as extracting agent.Meanwhile,n hexane was adopted for defatting treatment.The chromatographic separation was performed on an HPH-C18 column(2.7 μm，100 mm×2.1 mm) by gradient elution,with water containing 0.2% formic acid-acetonitrile as mobile phases at a flow rate of 0.35 mL/min.The 31 alkaloids were analyzed in positive electrospray ionization mode under multiple reaction monitoring(MRM) mode.Results showed that there were good linear relationships for the analytes in corresponding concentration ranges,with their correlation coefficients(r) of 0.992 8-1.000 0.The limits of detection(LOD) and limits of quantitation(LOQ) of the method were in the ranges of 0.09-3.03 μg/kg and 0.31-1012 μg/kg,respectively.The recoveries at three spiked levels ranged from 63.3% to 126%,with relative standard deviations(RSD) of 0.73%-17%.The method was rapid,accurate and sensitive,and was suitable for the detection of alkaloids in cosmetics and evaluation of safety of cosmetics.