WEDM is a kind of numerical control machining machine tool which uses continuous moving thin metal wire (called electrode wire, generally copper wire and molybdenum wire) as electrode to carry out pulse spark discharge on the workpiece to generate high temperature above 6000 degrees, remove metal and cut it into workpiece. WEDM is a machine tool with high degree of mechanical automation among CNC machines. In WEDM, there is a phenomenon of soft voltage discharge between the wire electrode and the workpiece with poor contact.