Abstract: The essential oil of leaves of Rhododendron dauricum L. is examined by GC-MS-DS, using a 35 × 0.3 mm i.d. glass capillary column coated with PEG-20M connected to a JEOL JMS-D300 model mass spectrometer. The column temperature is programmed from 80℃ to 180℃ at 2℃/min. Kovats retention index systems were determined with a PEG-20M capillary column for confirming the analytical results of mass spectrometry 24 compounds are indcntified, the major components are humulene, γ-elemene, cis-4, 11, 11-trimethyl-8- methylene-bicydo (7,2,0) undeca-4-ene γ-selinene, germacrone and juniper camphor. The superiorities and drawbacks of GC-MS analysis for essential oli are discussed.