Abstract: For the poor welding process stability in double pulse MIG welding-brazing of aluminum to steel, an evaluation method of welding process stability based on the concentration of tracks of U-I dynamic operating points was proposed. The concentration of tracks of U-I dynamic operating point is represented by the area of U-I diagram quantitatively computed by MATLAB in this method. The smaller the area of U-I diagram is, the more concentrated the U-I operating point tracks are, the more stable the welding process will be; otherwise, the greater the area of U-I diagram is, the more dispersed the the U-I operating point tracks are, the more unstable the welding process will be. The results show that the welding process stability at different welding positions obtained by this method is consistent with the analyses of welding voltage variance, probability density distribution of welding voltage and arc profile stability. As a result, this approach is reliable and provides a quantitative guidance in welding process stability evaluation of double pulse MIG welding-brazing of aluminum to steel.