Objective: To study the chemical constituents of the volatile oil from Bulbophyllum odoratissimum . Method: The chemical compositions of the volatile oil of the plants which were obtained by organic-steam distillation with hexane were analyzed by GC-MS. The constituents were identified by their mass spectra. The relative percentage of the oil constituents was calculated from the GC peak areas. Result: Thirty-eight kinds of chemical components were identified from B. odoratissimum. The amount of the identified components was accounted for 91.448% of all the volatile oil. The constituents whose relative content was more than 2% were determined as Z-9-octadecenal (18.075%)

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4-Di-tertbutylphenol (3.264%)

palmitic acid (5.413%)

oleic acid (25.079%)

tricosane (6.344%)

tetracosane (3.768%)

1-Monoolein (2.416%)

1-monolinolein (4.953%)

pontacosane (4.332%)

hexacosane (3.387%)

heptacosane (3.841%)

octacosane (3.102%). Conclusion: The composition of volatile oils from B. odoratissimum by GC-MS.