The effects of interaction between substrate moisture and light intensity on the growth,photosynthetic characteristics and soluble sugar content of the annual Dendrobium officinale were studied.The results showed that different substrate moisture and light intensity significantly affected the growth characteristics of Dendrobium officinale.Different substrate moisture under the same light intensity had significant effect on the content of Chla,Chlb,Chl(a+b) and Car,but had no significant effect on the ratio of Chl(a/b).Different light intensity under the same substrate moisture had significant effect on the content of Chla,Chlb,Chl(a+b),Car and the ratio of Chl(a/b).Pn,Gs,Tr and Ci were remarkably influenced by different substrate moisture and light intensity.Pn,Gs,Tr decreased remarkably when the light intensity was too high or too low.The content of soluble sugar was remarkably influenced by different substrate moisture and light intensity,which increased remarkably as substrate moisture decreased under the same light intensity,or as light intensity increased under the same substrate moisture.Among all the treatments, Dendrobium officinale grew best under 240 μmol/(m2·s) light intensity and 70% water-holding capacity of substrate.Content of soluble sugar increased to the top under 360 μmol/(m2·s) light intensity and 40% water-holding capacity of substrate.