Ethnopharmacological relevance: Decoction is the most common form of administering traditional Chinese med-icine (TCM). During the preparation of decoction, the high temperature and complex chemical environment result in the formation of complex and multiple phases. The differences in drug components in different phases induce gastrointestinal absorption and physiological response. Nux vomica (Strychnos nux-vomica L) is a typical toxic TCM used in China, with remarkable pharmacological activity. In order to reduce its toxicity, nux vomica (NV) is often decocted with Glycyrrhiza glabra (GG) in clinic, and the detoxification mechanism has always been the focus of research interest. Most studies investigated the compatibility of NV-GG, but the in vivo behavior of individual constituents based on phase state has yet to be elucidated.Aim of the study: To investigate the pharmacokinetic behavior of typical toxic components in different phase states of NV-GG decoction in rat plasma. Materials and methods: The sediment, suspension, colloid and true solution of NV-GG decoction was obtained via physical methods. The main components in different phase states were analyzed via reliable UFLC-Q-TOF-MS high-resolution mass spectrometry. A rapid and accurate HPLC-qqq-MS/MS method was established and vali-dated for accurate determination of brucine and strychnine levels in plasma, followed by pharmacokinetic evaluation of different phase states of NV-GG decoction in rats. Kinetex F5 100A (50 mm x 3.0 mm, 2.6 mu m) column was used for chromatographic separation. Aqueous solution containing acetonitrile and 0.1% formic acid was used as the mobile phase, followed by gradient elution at 0.4 mL/min. Mass spectra were detected by electrospray ionization (ESI) multiple reaction monitoring (MRM) in positive ion mode. Results: Fifteen different alkaloids were detected in different phase states of NV-GG decoction . Strychnine and brucine, which are toxic components with high content, were selected for quantitative analysis. The established UPLC-qqq-MS/MS method is accurate and reliable with a good linearity (R-2 > 0.99) in the respective concentration range, satisfying the quantitative requirements. The pharmacokinetic parameters of different phase states of rats differed significantly after gavage. The deposition phase was the most prominent. The index components showed higher C-max, AUC0 and T-max, while the T-1/2, MRT, V/F and CL/F were the smallest, with a relatively slow plasma clearance rate in rats. The true solution group showed the lowest T-max and the fastest absorption. Conclusion: This method has been successfully utilized to study the pharmacokinetics of different phase states of NV-GG decoction . Among the four phases, the deposition phase contributed to a large proportion of the in vivo kinetic behavior similar to that of sustained-release preparations, with slow absorption of toxic components and prolonged peak time. The pharmacokinetic parameters and plasma concentration-time curves of each phase can be used to study toxicity reduction of NV-GG and increase its biocompatibility.