OBJECTIVE To conduct a rapid qualitative study on the chemical constituents of the methanol extract in Thamnolia subuliformis (Ehrh.) W.Culb. by UHPLC-Q-Exactive Focus-MS/MS. METHODS The chromatographic separation was performed on a Waters Acquity UPLC BEH C18(2.1 mm×50 mm, 1.7 μm) column with acetonitrile(A)-0.1% formic acid aqueous solution(B) as mobile phase for gradient elution, the flow rate was 0.3 mL·min–1 and the column temperature was 30 ℃. Mass spectrometry was performed using an electrospray ionization and data was collected in negative ion modes, and the detection range was m/z 80−1 200. The chemical constituents in Thamnolia subuliformis (Ehrh.) W.Culb. were identified rapidly and comprehensively based on the accurate relative molecular and combined with literature data and reference substances. RESULTS A total of 39 chemical constituents were speculatively identified, including 9 mono-substituted phenyl rings, 11 depsides, 5 depsidones, 2 dibenzofuran, 10 lipids, and 2 others. CONCLUSION The chemical constituents in the Thamnolia subuliformis (Ehrh.) W.Culb. can be identified accurately and rapidly by this method. Among them, 3 compounds(β-resorcylic acid, usnic acid, atranorin) are unambiguously identified by comparing with reference standards, 19 compounds are found from Thamnolia subuliformis (Ehrh.) W.Culb. for the first time. This paper can provide the important basis for study on pharmacodynamic material and substitute development of Thamnolia subuliformis (Ehrh.) W.Culb..