Abstract: The microstructure of the fusion zone and the changing rule of the carbon-enriched zones in aging 0Cr6Mn13Ni10MoTi/1Cr5Mo dissimilar welded joints were studied by optical microscope and scanning electron microscope (SEM). It is found that the carbon-enriched zone, to a certain extent, initially forms in austenitic steel adjacent to the weld interface in the fusion zone. With increasing the aging time, the carbon-enriched zone gradually increases. After it reaches the maximum it begins to decrease and goes to disappear finally. The changing rule of carbon-enriched zone width is different from the past A302/1Cr5Mo dissimilar welded joints.