Abstract: By means of the double hole microshear equipment to measure local mechanical properties, the microshear experiments were carried out within the various zones of the aluminum alloy welded joints.In the experiment the load displacement was instrumentally recorded, meanwhile, the deformation of material being measured, the initiation and propagation of the crack in the material, and the final fracture were observed by a microscope.Then, combining the calculations of finite element mode of double holes microshear and the load-displacement curve obtained from the test, the fracture strains for the crack initiation were estimated.The determination results show that the fracture strain in the welds is lower than that in the base metal, and the fracture strain in the HAZ gradually increases as position is further from the fusion line.