Dendrobium candidum has important medicinal value, but with limited resources, so it has great significance to its full development and utilization. In this study, the extraction of polysaccharide from Dendrobium candidum was assisted by αLrhamnosidase. The extraction rate of Dendrobium candidum polysaccharide was improved by optimizing three factors, including temperature, time and enzyme quantity. The results showed that the polysaccharide extraction rate reached the maximum (38.4%)at 40  ℃, 1 h with 2.5% enzyme quantity and 21.7% without enzyme treatment. At the same time, the effects of αLrhamnosidase on the volatile constituents of Dendrobium candidum were analyzed by HSSPMEGCMS. GCMS analysis indicated  that 31 kinds of volatile components were found and the main constituents were hexanal, 1octen3ol, isomenthol and 3octen2one. The relative content of aldehydes in the sample were the highest and 6 kinds of new volatile components were produced after enzyme treatment. The results showed that αLrhamnosidase has a positive effect on the extraction rate of polysaccharide from Dendrobium candidum, which provides a basis for the research and application of Dendrobium candidum polysaccharides, also gives some references for the research and development of the volatile components of Dendrobium candidum