Abstract: Technology, Beijing 100022, China). Laser-arc hybrid welding is one of the advanced joining techniques.By using instruments such as a high-speed camera and a laser power meter, the effects of a vertically incident CO₂ laser beam on characteristics of a DC tungsten inter-gas arc are investigated.Results demonstrate that the laser-arc interaction causes the curve of arc static characteristic to shift downwards, the arc column to expand, the electric power to decease and the total arc power increase.With the increase of the laser power, the downward shift of the static characteristic curve increases, but the total arc power increases.The lower the arc current is and the nearer the laser beam locates to the cathode, the more the arc voltage decreases, which the expansion of the arc column mainly occurs in the range between the laser beam location and the anode.