Objective： The fatty acid composition and content of three kinds of Dendrobium were studied in order to provide reference for the development of dendrobium efficacy. Methods： The fatty acids compositions of Dendrobium nobile, Dendrobium officinale and Dendrobium chrysotoxum from different regions were systematically quantified by gas chromatography-mass spectrometry （GC-MS）, and a series of Odd-carbon fatty acids （OCFA） containing 15～23 carbons were found in all dendrobiums. Results： The results showed that the OCFA accounted for more than 8% of the total fatty acids. The relative abundances of OCFA from high to low were C_15:0, C_17:0, C_23:0, C_19:0 and C_21:0. C_15:0/C_17:0 （C_15:0 and C_17:0 relative abundance ratios） in D. nobile and D. officinale were less than 1.6 and more than 1.8, respectively. It was concluded that orchids contain a series of OCFA as one of the features in this family plants. Conclusion： The existence of OCFA in Dendrobium may be related to their drug activities.