Abstract: The influence of transverse current on seam formation of CO₂ laser beam welding of Aluminum alloys has been investigated. In the experiment, two tungsten electrodes set on both sides of weld pool provide transverse current to the pool. The experiment results show that when the transverse current is applied, the wele depth and weld width increases with the current, but the depth increases more obviously than the width; The change of weld depth and weld width is only related with current value but has little to do with the direction of current.