Abstract: 【Objective】 To provide a theoretical basis for the development and utilization of Thuja resources, the composition of essential oils from leaves of five Thuja species were analyzed. 【Method】 Healthy 4-year-old seedlings, having the same size and with consistent growth patterns, of five Thuja species were selected as study materials. The volatile components of new leaves in the same position of seedlings from all five species were extracted by solid-phase micro-extraction(SPME), separated and identified by gas chromatography-mass spectrometry(GC-MS). Qualitative analysis was carried out by mass spectrometry and the relative contents of the volatile components were calculated by peak area normalization. 【Result】 One hundred and thirty-six essential oils were detected; 41, 48, 40, 41 and 36 were identified from Thuja sutchuenensis, T. koraiensis, T. standishii, T. occidentalis and T. plicata, respectively. The volatile components of all five species were dominated by monoterpenes, and the average relative monoterpene content was 61.154%; the highest and lowest contents were found in T. plicata (78.669%)and T. koraiensis(49.451%), respectively. The composition and the relative content of the essential oils were significantly different among the five congeneric species. Only three components, γ-terpinene, α-thujone and(8β,13β)-13-methyl-17-norkaur-15-ene, were shared by all five species. Terpinolene, α-caryophyllene, methyl hexadecanoate, and α,α,4-trimethyl-3-cyclohexene-1-methanol, acetate, were found in four species. The common components of the essential oils differed among the five species, and only α-thujone, which was generally present at high levels, was found in all Thuja species. Seventy-five components were only identified in only one of the five species; 18, 23, 11, 12 and 11 unique components were found in T. sutchuenensis, T. koraiensis, T. standishii, T. occidentalis and T. plicata, respectively, and longifolene(4.950%), myrtenyl acetate(2.759%), 1-methyl-4-(1-methylethyl)-1,3-cyclohexadiene(0.678%), β-pinene(4.232%), and estragole(0.963%)were the unique components with the highest content in each species, respectively. 【Conclusion】 The volatile components of five Thuja species were dominated by monoterpenes, and the relative contents of essential oils from leaves differed significantly among the five species, but the α-thujone content was the highest in all five species.