Abstract: The butt-welding tests of 4 mm thick 6061-T6 aluminum alloy plate were carried out by using laser self-fusion welding.Metallographic microscope, X-ray diffractometer and scanning electron microscope were used to analyze the macro-morphology and microstructure of the welded joints.The mechanical properties of the welded joints were tested by microhardness tester and universal tensile testing machine.The results show that the laser welding parameters have a significant effect on the macro-morphology of 6061-T6 aluminum alloy welded joints.The weld with good formation and low porosity can be obtained by using appropriate laser parameters.The optimized welding parameters are laser power of 4.8 kW, welding speed of 30mm/s, defocusing amount of -1 mm.The microstructure near the fusion line is columnar crystal growing perpendicular to the fusion line, the weld center is composed of fine dendrites, and the grain size is obviously smaller than that of the base metal.The microhardness curve of 6061-T6 aluminum alloy laser welding joints is close to "U" shape, and the microhardness of the weld center is the lowest, about 65HV.The fracture positions of the joint specimens are in the weld zone, and the maximum tensile strength of the welded joint reaches 71.7%of the base metal.The fracture type belongs to quasi cleavage fracture.