Abstract: This paper deals with the determination of chemical compositions of volatile oil of Cuminum cyminum L. in Xinjiang area. Using capillary gas chromatography and GG/MS, the following components have been identified: α-pinene, β-pinene, camphene, myrcene, γ-terpinene, ρ-cymene, terpinolene, linalool, pulegone, cuminaldehyde, 2,3-dihydrocuminal and myrtenal etc. Besides, silica gel column chromatography as well as some spectrum methods such as IR, MS, NMR, etc. were used to elucidate the structure of 2,3-dihydrocuminal or 4-isopropyldelta-1,3-cyclohexadiene-l-carbaldehyde.