A method of gas chromatography-mass spectrometry(GC-MS) with steam distillation(SD) and supercritical CO2 extraction(SC-CO2) was developed for the analysis of components of essential oil in leaves of Zanthoxylum piperitum ‘Odorum’.The samples were extracted by SD and SC-CO2,respectively,then analyzed by GC-MS. The quality of extracts was distinguished by determining the scavenging ability and reducibility for free radical DPPH·.A total of 34 components,extracted by both SD and SC-CO2,were mainly lipids and alkenes.However,the types of components obtained by the two methods were significantly different.The SD extracted components,contained relatively high contents of ethyl benzene(43.15%),methyl cinnamate (30.33%),α-caryophyllene(1.81%) and α-myrcene(8.41%).In contrast,the SC-CO2 method mainly yielded methyl cinnamate (73.91%),limonene(11.13%) and α-caryophyllene(4.12%).As the scavenging ability for DPPH· was concerned,the essential oils extracted by SC-CO2 reached the butylated hydroxytoluene(BHT) inhibition rate of 97.27% at the concentration of 8 mg/mL,with an IC50 of 3.173 3.At 20 mg/mL,their reducibility reached to 34.86% of that of vitamin C(Vc).In contrast,the SD extracted essential oils only had a BHT inhibition rate of 14.27% at 20 mg/mL,and 5.98% of Vc reducibility.Therefore,the differential components between the two extraction methods were mainly those reductive and antioxidative substances such as phenols and terpenes.In conclusion,the essential oils extracted from leaves of Zanthoxylum piperitum by SC-CO2 contained more insect repelling and antimicrobial agents,and its extraction effects were superior to those of SD method.