Abstract: This paper deals with the effect of light with various wavelengths on the callus growth and bud formation of Begonia rex-cultorum Bailey in vitro. Results show that:l. bud formation and callus growth are inhibited by red and yellow lights; 2. blue light is indispensable for callus growth and bud formation, and the effect of white light and dark is similar; 3. fewer and lighter buds are formed under green light than under blue one.