The leaf oil of sweet orange (Citrus sinensis (L.) Osbeck), namely three culticars "Cam chanh", "Cam Chiu nhiet" and "Cam Van du" in Nghe An province was obtained by steam distilation. The chemical components of essential oil were analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS). The results showed that there were fourty eight components identified. In which, the principal components were mono terpene hydrocarbons. The main constituents of essential oil were found to be sabinene (24.85-34.45 percent), linalool (9.95-12.25 percent), limonene (7.13-9.80 percent), (Z)-beta-ocimene (6.80-8.87 percent), delta-carene (3.08-4.07 percent), E-citral (geraniol) (6.99-10.66 percent), Z-citral (neral) (1.65-2.63 percent), beta-caryophyltene (2.52-3.40 percent), spathoulenol (alto) (3.08-5.11 percent) and beta-sinensal (4.20-6.75 percent).