The invention discloses a self-adaption tension control device and method of electrode wires of a linear cutting machine. The device comprises a rack, a wire storage cylinder, transition reversing wheels, an upper machine head and a lower machine head; the wire storage cylinder is arranged on the rack, and the upper machine head and the lower machine head are each provided with a main guide wheel; the electrode wires, wound on the wire storage cylinder, all the reversing wheels and the guide wheels form a wire winding loop, and the position, arranged between the upper machine head and the wire storage cylinder, of the rack, and the position, arranged between the lower machine head and the wire storage cylinder, of the rack are each provided with a shaft type tension sensor; each shaft type tension sensor is provided with a tension detection wheel through a bearing, and the electrode wires are wound on the two tension detection wheels to form wrap angles; each shaft type tension sensor is connected with a single chip microcomputer; two parallel guide columns and a lead screw and nut pair are arranged on the rack, and a lead screw is mounted on the rack and is parallel to the two guide columns; a servo motor is connected with the lead screw through a synchronous belt wheel mechanism, and a sliding seat is fixedly connected with the nut and is arranged on the two guide columns in a sliding manner; a tensioning wheel is arranged on the sliding seat, and the electrode wires are wound on the tensioning wheel. According to the device, tension of the electrode wires on the machining segment can be more precisely detected and adjusted, and therefore the machining quality is improved.