Abstract: Tint etching technique was used to reveal the microstructure of the fusion zone of the welded joint,specifically to reveal the fusion zone of ferritic-austenitic dissimilar metal joint.It is known that the researches on the fusion zone of the F/A dissimilar metal have been done since 1940's,but because of the unsuitable etching method and the mismatch of the chemical compositions between the two kinds of metals the structure in the fusion zone were not clear,this region was often called "light etching region".The tint etching technique has exellent advantage of revealling the structures in this region.By elaborating the tint etching agent the structures of the fusion zone were claarly shown.It can also increase the distinguishability and contrast in revealling the structures of low alloy steel welded joint.