Due to its superior properties, such as low density, high specific strength, excellent corrosion resistance, and good formability, aluminum alloy has become the main material for the light-weight manufacturing of high-speed train body. With the characteristics of low heat input, high welding speed, and high process stability, laser-MIG hybrid welding is a promising joining technology for the high-speed train aluminum alloy body with the features of low deformation, high efficiency, and high quality. In the present work, the welding characteristics of laser-MIG hybrid welding for 6 mm thickness 6082-T6 aluminum alloy was studied. The effects of welding parameters on the weld formation and porosity defects were investigated. The microstructure features, micro-hardness distribution, and mechanical properties were also researched. The results indicated that the full-penetration weld could be performed free of porosity in a wide range of laser power. The MIG current arc significantly affected the porosity positions, and the porosity mainly existed near the fusion line of when the MIG current greater than 150 A. The content and size of the porosity both increased as the welding speed increasing. It was beneficial for the reduction of the porosity rate when the heat source distance was around 3 mm, or the gas flow rate less than 25 L·min-1. The weld microstructure has consisted of the equiaxial crystal zone, columnar crystal zone, partly melted zone, and over-aging zone. The widths of the partly melted zone and over-aging zone in the arc affected zone were larger than that in the laser affected zone. There were two obvious softening areas in the heat affected area, which were located near the fusion line and 24 mm away from the fusion line. The average tensile strength of the joint was 255.1 MPa, which could reach up to 82.3% of the base material. The fracture occurred in the heat-affected zone, and the fracture propagation path was basically parallel with the fusion line. The fracture appearance of the laser-MIG hybrid welded joints belonged to the ductile fracture.