5083 aluminum alloy is widely used in shipbuilding and high speed train manufacturing industry. The main problems, such as sag and undercut, occur during fiber laser welding of 5083 aluminum alloy. To overcome these problems, 5083 aluminum alloy with the thickness of 4 mm is welded using 5087 filler wire in our present work. The effects of welding parameters on the weld forming are studied in details. And the microstructure and mechanical properties of joints are also investigated. The result shows that fiber laser welding with filler wire can effectively avoid the weld surface depression and undercut defects by choosing suitable processing parameters as power of 6 kW, welding speed of 7.5 m/min, wire feed rate of 4.5 m/min, distance between laser and wire of 1.0 mm, and also gets a good joint forming with fine grain weld. The average tensile strength of the joint with filler wire is 304 MPa, about 88% of the parent material, which is also about 6.17% higher than that of the autogenous weld. The average elongation of 5.43 % with filler wire is found, which increases by 52% than that of the autogenous joint. After the transverse tensile test, the joint with filler wire is fractured along the weld, which shows the ductile characteristics.