Abstract: Due to the fact that the parameter variety adaptability to MIG welding process was not sufficient in conventional digital PI control, an algorithm of adaptive control of on-line integral parameters was proposed. The control algorithm could obtain optimized integral parameters quickly and automatically by real-time detecting control quantity. Based on the control algorithmand the inherent minimum times of the rising edge and falling edge of the welding current, integral parameters can be divided into rising edge parameter and falling edge parameter. The adaptive controller for integral parameter was designed and implemented inside the welding equipment. The result indicated that using this algorithm and controller different initial values of integral parameters could be quickly searched for the adaptive value and a stable welding process can be achieved.