Abstract: Tb-Dy-Fe twin crystal or polycrystal magnetostrictive materials are normally employed as driving unit in magnetostrictive actuator,yet the crystal boundary and twin crystal structure in the Tb-Dy-Fe materials hinder the movement of domain walls so that the displacement output under low magnetic field is rather small.This problem could be effectively solved by using Tb-Dy-Fe single crystal as driving unit.The design of a prototype actuator with use such kind of high performance RFe 2 single crystal is described covering the detail structure and the numerical current source.