Abstract: As for the electrode wire of the Meidum-speed WEDM machine tool, its tension decreases with the increase of processing time, which leads to problems such as short circuit, cutting stop, and surface quality decline.Here, an external adjustable tension tightening wire mechanism is developed, which only forms a circuit with the wire moving system when the wire is tightened, so as to solve the problem of insufficient tension in the process of processing, especially the large amount of wire tightening when the new wire is applied.The practice has proved that the roughness of the machined surface can be reduced by about 30% by using the adjustable tensioning mechanism, which can effectively improve the machining quality and efficiency of the workpiece.