In the reciprocating wire electrical discharge machining (WEDM) process, it is normal problem that loosening wire tension in one transporting direction, difficult to control wire tension, major fluctuations of wire tension in two transmission directions, thus these phenomena have a strong impact on efficiency, precision and stability. According to this situation, a new method of transporting wire was proposed, and adaptive control algorithm was adopted, then a closedloop control system of stabilizing wire tension was developed. The practice machining data indicated that the wire tension is adequately controlled by this presented control system, its amplitude is controlled less than ±04 N, and the vibration and deflection phenomena are significantly decreased, and the using performance of WEDM is greatly improved.