Dendropanax dentiger root is a traditional medicinal plant in China and used to treat inflammatory diseases for centuries, but its phytochemical profiling and biological functions are still unknown. Thus, a rapid, efficient, and precise method based on ultra high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UHPLC-Q-TOF-MS/MS) was applied to rapidly analyse the phytochemical profiling of D. dentiger with anti-inflammatory and antioxidant activities in vitro. As a result, a total of 78 chemical compositions, including 15 phenylpropanoids, 15 alkaloids, 14 flavonoids, 14 fatty acids, 7 phenols, 4 steroids, 4 cyclic peptides, 3 terpenoids, and 2 others, were identified or tentatively characterized in the roots of D. dentiger. Moreover, alkaloid and cyclic peptide were reported from D. dentiger for the first time. In addition, the ethanol crude extract of D. dentiger roots exhibited remarkable anti-inflammatory activity against cyclooxygenase- (COX-) 2 inhibitory and antioxidant activities in vitro. This study is the first to explore the phytochemical analysis and COX-2 inhibitory activity of D. dentiger. This study can provide important phytochemical profiles and biological functions for the application of D. dentiger roots as a new source of natural COX-2 inhibitors and antioxidants in pharmaceutical industry. © 2020 Li Yang et al.