Abstract： Aimed at the selection of the multi-focus image fusion rule of double arc welding of magnesium alloy, a fusion rule was proposed based on windows for choosing wavelet low frequency coefficient. The fusion rule gave full consideration of the contribution of the low frequency component to the fused image and the correlation between image pixels. To the experimental results and objective evaluation indicates that the proposed algorithm can have a better fusion effect, a clear object and fusion pool edge information of the multifocus image fusion of double arc welding of magnesium alloy.