Ginsenosides are known as the principal pharmacological active constituents in Panax medicinal plants such as Asian ginseng, American ginseng and Notoginseng. Some of the ginsenosides, especially the 20(R) isomers, are trace in natural source and difficult to be chemically synthesized. The present study provides an approach to produce such trace ginsenosides applying biotransformation through E.coli modified with relevent genes.