The electrostatic field induced jet (E-Jet) machining is a novel type of electric machining method. In this method, the fine jet with induced charge on its surface jetted from the tip of the Taylor cone in the intense electrostatic field, and the debris can be removed by the discharge between the tip of the fine jet and the workpiece in micro scale. For the discharge appears extremely fast, it is difficult to confirm the governing mechanism of this machining process. Therefore, this paper has utilized different kinds of liquid such as deionized water, 2% NaCl solution and 2% NaOH solution to form the fine E-jet to machine the workpiece under different polarities. The experiment results show that these solutions can successfully machine the workpiece under different polarities. The SEM results and the composition analysis confirm that it is the E-Jet EDM that machined the workpiece in the cathode polarity machining and it is the E-Jet EDM and electrochemical machining (ECM) compound machining method that removed the debris from the workpiece in the anode polarity machining.