Studies the S355 J2 W+N microstructure in S355 J2 W+N welded joint by repair welding,analyzes the characteristics of weld zone and heat affected zone through different times of repair welding. The results show that the microstructure of upper layer and the bottom are not influenced apparently by repair welding. As the increase of the times of repair welding pearlite in the weld metal tapers,ferrite grain grows up. When welded by the same times,from top to bottom along the thickness of the joint direction,HAZ acicular ferrite in the coarse grain zone has a tendency to reduce,HAZ incomplete uneven grain size are normalized area,the organization has kept rolling state characteristics of the parent metal.