Abstract: Aiming at 3 mm aluminum alloy profiles of rail transit, laser-arc hybrid welding process was used to study influence of misalignment and assembly gap that often appeared in the production process on weld quality. The results showed that laser arc hybrid welding had stronger adaptability to welding conditions of aluminum alloy profiles in rail transit. Under the test conditions, assembly gap mainly affected reinforcement of weld and tensile strength of welded joints. With the increase of assembly gap, reinforcement of weld decreased until concave appeared, which reduced tensile strength of welded joints. Increase of misalignment would lead to more spatter on the surface of weld, while misalignment had no obvious effect on porosity of weld and tensile strength of welded joints. Under the test conditions, formation of weld, porosity, metallographic microstructure and tensile strength of welded joints by laser-arc hybrid welding met production requirements within 0.5 mm assembly gap and misalignment.