To clarify the chemical constituents of alcohol extract from Thesium chinense Turcz.,ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS/MS) was analyzed in this study.The molecular ion peak information was analyzed by Mass Hunter B.07.00 data processing software.The molecular formula with error within 5×10^-6 was compared with the TCM database to identify the compounds,combined with reference the related literature and control comparison,combining the precise relative molecular mass and mass spectrometry fragment information.A total of Fifty four chemical compounds in T. chinense,The main chemical constituents included 16 flavonoids,10 alkaloids,5 diterpenes,5 organic acids and other compounds.Twenty-five compounds such as oxymatrine, 4-O-feruloylquinic acid,quercetin-7-O-glucopyranoside,and quercetin-3-O-neohesperidoside were identified in this genus for the first time.The mass fragmentation pattern of alkaloids,flavonoids and diterpenes was further explored.Using UPLC-Q-TOF-MS/MS technology can quickly and accurately identify the alcohol extract of chemical constituents from T. chinense,which will expand new ideas for further clinical application,and will provide the scientific theory basis for its clinical application and quality control.