In order to further improve the quality of volatile oil samples from Miao medicine the roots of Valeriana officinalis var. latifolia and provide scientific basis and method for its essential oil evaluation,GC-MS was applied for the analysis of essential oil to identify 25 chemical constituents.The relative contents of each constituent in the oil was determined by area normalization.In addition,the methodological study of 3 major constituents (bornyl acetate,camphene and isobicyclogermacrenal) was conducted with a GC system.Method validation results showed good linearity,stability,precision and a high sample recovery rate.The content of borneol acetate,camphene and isobicyclogermacrenal in 16 batches of volatile oil samples from different regions in Guizhou Province ranged from 34.02% to 46.70%,13.09% to 18.93%,and 7.44% to 15.18%,respectively.This was the first time to isolate and identify isobicyclogermacrenal from the volatile oil in Valeriana officinalis var. latifolia.Three high content components were selected to evaluate the quality of the volatile oil,which could lay a solid foundation for the development of the quality standard of the volatile oil.