Abstract: The Al-Mg-Mn alloy sheets as cold-rolled state were welded by laser beam welding. Then X-ray diffraction and finite element simulation methods were used to evaluate the welding residual stress and strain. Results show that the established finite element model is suitable for the laser welding. In the weldment,residual stress is mainly distributed in the middle and both ends,the range of stress perpendicular to the direction of the weld is low,the strain occurs mainly in the weld and its vicinity.