Diosgenin, as a typical kind of steroids, is an important industrial material for the synthesis of many steroidal saponins that have a broad market of androgenic,contraceptive,anti-inflammatory, and estrogenic drugs and so on[1].Chemical synthesis would provide a feasible way to obtain homogeneous saponins, but the protection and the de-protection of hydroxyl groups are ineluctable processes[2], during which the environment would be undermined by expensive organic solvent used heavily.So the more economic and less contaminative route is enzymatic synthesis which follows the biosynthetic pathway.