Cymbidium sinense is a traditional orchid in the tropical and subtropical regions of Asia, and it has attracted attention because of its fragrant flowers and graceful leaves. Essential oils were extracted by simultaneous distillation-extraction (SDE) from the flowers of six cultivars. GC-MS analysis revealed fifty compounds, constituting 78.40-97.96% of the total essential oils. The main constituents were farnesyl alcohol (0.66-12.51%), n-tetracosanol-1(1.07-7.77%), dihydro-β-ionone (0.34-13.16%), β-ionone (0.37-20.23%), pentacosan (10.28-17.51%), heptacosane (6.43-11.90%), α-ionene(2.89-9.14%), tricosane (5.30-8.86%), p-cresol (0.96-6.32%), n-hexadecanoic acid (1.81-6.72%) and linoleic acid (0-16.86%). ‘Baizui baimo’ seemed to be the richest cultivar in alcohols (20.28%) and ketones (33.77%). Six cultivars were separated into 3 chemotypes by hierarchical cluster analysis, according to the composition of the corresponding essential oils. The principal component analysis (PCA) also revealed chemical polymorphism in the essential oils of the C. sinense flowers, which could be attributed to genetic factors. This work represents the first study of essential oils from C. sinense flowers, and it gives further knowledge for exploitation and application of this orchid resource.