This study aims to investigate the chemical constituents of mastic and screen their anti-inflammatory activities. Compounds were isolated and purified from the methanol-ethyl acetate extract by various chromatographic techniques, along with semi-preparative HPLC. Their structures were elucidated by MS, NMR, ECD and comparisons with the data reported in the literature. Seven oleanane-type triterpenoids were identified as (5R,8R,9R,10S,14S,17S,18S)-17β-formyloxy-28-norolean-12-ene-3,11-dione (1), (3S,5R,8S,10S,14R,17S,18S)-3β-hydroxy-9(11),12-oleanadien-28-hydroxymethyl (2), juglangenin A (3), 3-oxo-11α-methoxyl-12-oleane-28-oic acid (4), 3-oxo-11α,12α-epoxyoleanan-28,13β-olide (5), 13β,28-epoxy-3β-hydroxy-olean-11-ene (6), and 11,13(18)-oleanadien-28-hydroxymethyl-3-one (7). Among them, compounds 1 and 2 are new compounds, and all the compounds were isolated for the first time from mastic. The anti-inflammatory activity was evaluated using the lipopolysaccharide (LPS)-induced mouse macrophage (RAW 264.7) model. The results indicated that compound 1 significantly inhibited the production of NO in RAW 264.7 cells induced by LPS, with an IC₅₀ value of 7.44±0.49 μmol/L, which is stronger than that of the positive control, dexamethasone, with an IC₅₀ of 9.93±1.17 μmol/L. Compound 3 showed comparable anti-inflammatory effects to dexamethasone, with an IC₅₀ of 9.63±2.47 μmol/L. The remaining compounds showed weaker anti-inflammatory effects than dexamethasone, with IC₅₀ values ranging between 12.62 and 19.74 μmol/L.