Abstract: Based on the trial of twin-spot laser welding of 2 mm thick 1420 Al-Li alloy,the effect of laser welding parameters including laser power,welding speed,defocusing distance and twin-spot adjust parameters including focus spacing,focus orientation,intensity distribution of the foci on the formation of the joints was studied.The characteristics of weld formation in single-spot and twin-spot welding were compared and analyzed.The results indicated that the process window in twin-spot laser welding was narrower than in single spot laser welding,but the weld quality was improved prominently.The effect of focus spacing on the weld formation was related to intensity distribution of the foci,which had an essential influence on the welding result.In order to get a higher penetration and failure free seams,a 40% to 60% and a 60% to 40% distribution were better.Furthermore the focus orientation had another slight impact on the welding result.