Abstract: The chemical composition of essential oil from Citrus sinensis was investigated by gas chromatographymass spectrometry( GC- MS). Its minimum inhibitory concentration( MIC) was determined by inhibition zone experiment and tube double dilution method. The antioxidant activity of citrus sinensis essential oil was comparatively studied by DPPH,ABTS and ferric reducing antioxidant power and ferrous ions chelating capacity.The results showed that 101 components were detected in the essential oil and 50 compounds were identified.The major compounds included aliphatic compounds( 5.96%) and terpenoids( 78.39%). The essential oil revealed strong antibacterial activity,its MIC was 7.5 μL / m L against Bacillus subtilis,and 15 μL / m L against Trichoderma viride respectively.The citrus sinensis essential oil exhibited significant scavenging capacities against DPPH and ABTS+free radical and ferric reducing antioxidant power and ferrous ions chelating capacity all in a concentration- dependent fashion.