Abstract: The specimens were cut from weld metal in two orientations, and the micro-tensile test was conducted. The appearance of tensile specimens at different strains were observed with metallographic microscope, confocal laser scanning microscope and scanning electron microscope (SEM) to study the surface morphology and local deformation of specimens during tensile tests. What's more, the fracture morphology of specimens was observed with SEM. The results indicate that plastic deformation concentrates in proeutectoid ferrite in both kinds of specimens and the plastic deformation in PF is not homogenous; for vertical specimen, under the effect of strain concentration which is related to weak stress singularities, the crack starts in grain triple junctions; crack initiation districts of horizontal specimen have the characteristic of local brittle, the crack initiates by interfacial decohesion at proeutectoid ferrite /acicular ferrite interfaces, as a result of plastic deformation concentration in the interface of acicular ferrite and proeutectoid ferrite.