Abstract: In present work, the chemical ingredients of the essential oil of roots of Angelica Sinensis (Oliv.) Diels have been analyzed by capillary column GC/MS. 19, 12 and 6 compounds have been identified from the neutral, phenolic and acidic fractions respectively.Among them 32 constituents have not been found in this species before. By high resolution mass spectrometry and metastable ion scanning technique, the fragmentation pattern of ligustilide, a principal constituent of the essential oil, has been studied.