Abstract: The constituents of the Artemisia annua L. volatile oil from Yongdeng of Gansu were analyzed by GC/MS,MassworksTMsoftware and NIST library. There were 33 kinds of components determined in the Artemisia annua L. volatile oil, mainly for thujone, eucalyptus alcohol, isopropyl toluene, β- pinene, artemisia ketone,dipentene,camphor and so on. The results showed that MassworksTMtechnology had very important significance to provide accurate molecular weight information of unknown compound. It could provide a strong basis to identify unknown compounds which was obtained by the low-resolution quadruple mass spectrometer,and meanwhile could improve the reliability of spectral library search.