Abstract: In order to study the microstructure and property of butt joints of aluminum alloy 5A06,the butt joint of 2mm thick aluminum alloy 5A06 sheets was filled with SA1-Mg5 wire and welded with a 3kW Nd:YAG laser. The chemical elements in the welding seam were almost the same as those of the substrate. Its microstructure was fine,dense columnar crystals near to the fusion area and fine dendrites in the center, and the width of heat affected zone was only from 50μm to 100μm. The tensile strength and elongation were respective up to 93% and 58% of that of the substrate metal. The entire joint was broken in the heat affected zone, the scanning electron microscope observation showed that the fracture surface of 5A06 alloy and welded joint exhibited hybrid tough fracture of dimple and tear ridge. The results show that the butt laser welding aluminum alloy with appropriate component filler wire can erase the falling, undercut and sag which is inevitably with laser autogenous welding, and the property of joints is improved a lot.