The original bulbs of Dendrobium officinale were soaked in the mixture of different mass concentration colchicine (C₂₂H₂₅O₆) and 0.02 g·mL^-1 dimethyl sulphoxide (DMSO).The variant plants were identified in morphology,cytology,in order to obtain steady tetraploid plants and analyze its physiological characteristics.Results showed that:with 2.0 g·L^-1 colchicine and 0.02 g·mL^-1 DMSO mixed aqueous solution to deal with the original bulb for 36 hours,the plant induced rate could reach 20%.Copmared with diploid plants,the tetraploid plants became dwarf;its stems were thick and short;leaves were small and thick;stomata diameter were increased.The chromosome numbers of diploid cells was 2n=2x=38,while tetraploid cells was 2n=4x=76.With flow cytometry,the relative DNA content of tetraploid was 400,diploid was only 200.Tetraploid plants leaf chlorophyll,soluble protein,soluble sugar contents were higher than that of diploid,were 5.03,3.59,2.98 mg·g^-1,respectively;The main antioxidant enzyme POD and SOD activities in the leaves were significantly higher than that of diploid,were 9.08 and 180.4 U·mg^-1,and the tetraploid plants significantly reduced the accumulation of MDA content.This research show that:2.0 g·L^-1 colchicine and 0.02 g·mL^-1 mixed aqueous solution to deal with the original bulb lasting 36 hours can improve the success rate of induction,to reduce the proportion of chimeras.So,this combination is the best conditions.