Abstract: The growth of Dendrobium nobile is often stressed by zinc. To study the effect of zinc on the growth and biosynthesis of medicinal components, external zinc was regularly sprayed on Dendrobium nobile. The results showed that the net photosynthetic rate, transpiration rate, stomatal conductance, chlorophyll A and B of leaves increased first and then decreased with the increase of zinc concentration. At 400 μmol/L, they reached the maximum value, indicating that a certain dose of zinc could promote the photosynthesis of Dendrobium nobile. When the concentration of zinc was 400 μmol/L, which could promote the synthesis of SOD, the content of APX and AsA reach the maximum. The content of polysaccharide reached the maximum on the 7th day, the content of polyphenols reached the maximum on the 14th day. This result suggests that exogenous zinc can promote the accumulation of active components in Dendrobium nobile, and when the zinc concentration is 400 μmol/L, the promoting effect is greatest. While, it was found that the polysaccharide can combine with zinc well to form polysaccharide-zinc chelate, and transform inorganic zinc into organic zinc, which was stored in the form of polysaccharide-Zn in vivo and reduced the damage to Dendrobium nobile by Zn-stress