In order to develop the green manufacturing and microfabrication, an innovative micro-electrochemical machining (ECM) method¬¬-the electrochemical machining in pure water was studied. On the base of experimentation principle, ECM set up was developed for engineering application. Water dissociation mechanism is found under the function of cation exchange membrane, and many factors to enhance current density were analyzed. As a result of technological test, a micro hole is machined in the thin stainless. It is confirmed that electrochemical machining technology is feasibility to make use of pure water as electrolyte.