Abstract: AimTo analyze the chemical constituents of Cortex Moutan by liquid chromatography coupled with electrospray ionization mass spectrometry. MethodsAn on-line optimized HPLC-DAD/MS² technique was employed. ResultsIn the negative ion detection mode, 38 components such as monoterpene glucosides, galloylglucoses and acetophenones were isolated. Among them, over thirty compounds were identified, including paeonol, paeonilflorin, oxypaeoniflorin, benzoylpaeoniflorin, benzoyloxypaeoniflorin, galloylpaeoniflorin, galloyloxypaeoniflorin, mundanpioside A, C, D, E, H, etc. by the high performance liquid chromatography with diode-array detection in parallel with electrospray ionization and quadrupole-time of flight tandem mass spectrometry (HPLC-DAD/ESI-MS²). Conclusion This method can be used to rapidly determine the constituents of Cortex Moutan.