Abstract: Qualitative and quantitative analytical studies of the essential oil steam distilled from the rhizome of Ligusticum sinense Oliv. cv. Chuanxiong Hort., one of Chinese traditional drugs, were undertaken by means of a Sigma 2000 capillary gas chromatograph and a Dani 3800 GC-VG 7070E MS-VG 11/250 DS. Of the 180 peaks isolated by 50m×0.25mm (id) bonded methyl silicone fused silica column, 40 components which make up 93.64% of the total oil were identified by retention indices, authentic sample overlapping method, and mass spectral determinations. The relative content of the components in the essential oil were calculated by a LCI-100 integrator. The major components are ligustilide (58.00%), 3-butyl phthalide (5.29%), and sabinene (6.08%), etc.