Abstract: The chemical composition of the steam distillated essential oil obtained from twigs bark of Zanthoxylum ailanthoides was analyzed by gas chromatography-mass spectrometry (GC-MS),and antioxidant activities of the essential oil were analyzed. GC-MS analysis of the oil resulted in determination of 54 compounds. (-)-terpinen-4-ol (17.64%), eucalyptol(13.82%), sabinene (11.73%), γ-terpinene (10.88%), α-carene(8.00%), linalool(6.93%), terpinolene (5.86%), α-terpineol(4.44%) and (-)-α-phellandrene(2.25%) were determined as the major components.The inhibition percentages of superoxide anion free radical(O₂^·),hydroxyl free radical(·OH),DPPH radical and eliminating NO_2^- (scavenging activity) of the essential oil(400 ppm) were 17.4%,49.1%,48.7% and 50.8%,respectively.

Key words: Zanthoxylum ailanthoides, essential oil, chemical composition, antioxidant activities, GC-MS