Abstract: The constituents of essential oils which were extracted by hydrodistillation from fresh and dried leaves of Peristrophe baphica ,were analyzed by gas chromatography-mass spectrometry (GC - MS). Overall, 51 volatile components were identified on the basis of their mass spectra characteristics .Thirty-two compounds were identified in the oil of fresh leaves, comprising 98.81% of the total oil, in which trans-Phytol (43.29%), nerolidolcistrans （7.07%） ，caryophyllene（4.91%），methyl linolenate（3.81%） and phytone （3.74%） were the major constituents. Forty-two compounds, representing 96.23% of the total oil, were identified in dried leaves oil. Trans-phytol (33.5%) ,nerolidolcistrans (7.75%) , 1-octen-3-ol (7.20%)，caryophyllene(5.14%) ,phytone（4.74%）and camphor (4.07%) were the major compounds. The chemical compounds of the essential oils showed that there are only 23 common compounds between two parts. The relative contents of other chemical constituents were different.