Abstract: Ultra high performance liquid chromatography tandem linear ion trap orbitrap mass spectrometry (UHPLC-LTQ-orbitrap-MS) was applied to analyze and identify flavonoids and phenylethanoid glycosides in the Tibetan herb Lagotis brevituba Maxim. A method of data-dependent scan coupling with dynamic exclusion was developed for analyzing flavonoids and phenylethanoid glycosides under positive and negative ion mode of electrospray ionization (ESI). The compounds of Lagotis brevituba Maxim. were systematically identified through exact molecular mass, fragmentation patterns, retention time and reported references. A total of 167 compounds were detected, of which 84 were flavonoids and 83 were phenylethanoid glycosides, which greatly enriched the number and types of flavonoids and phenylethanol glycosides in Lagotis genus medicinal plants. Baohuoside Ⅰ, 4 disaccharide O-glycoside flavonoids (composed of deoxyhexose and glucuronic acid), 9 C-glycoside flavonoids, 15 tetrasaccharide phenylethanoid glycosides and 5 phenylethanoid glycosides with substituents on the β-position of the phenylethyl group were identified in Lagotis genus medicinal plants for the first time. This study provides scientific support for elucidating the material basis and improving the quality control of Lagotis brevituba Maxim.