A method and device for removing an electromagnetic core, the method including: using an electromagnet to magnetize or demagnetize a metallic upper nozzle when a magneto-conductive workpiece is cut off in a WEDM manner; attracting a core capable of being completely cut off and separated in the workpiece; utilizing the metallic upper nozzle to detect whether attracted; if the core is attracted, moving the core to a target area; demagnetizing and dropping the core in a trash area. The device is applied to a WEDM machine; after the metallic magneto-conductive upper nozzle is magnetized by the electromagnet, the upper nozzle is used to attract the magneto-conductive core; a metallic water spray cover is utilized to detect whether the core is attracted; the core is moved to the target area by a motion system of the WEDM machine, and dropped in a trash device after the upper nozzle is demagnetized.