Abstract: In the short-circuiting transfer process of CO₂ arc welding, the concept of load voltage-ampere characteristic curve and single cycle load voltage-ampere characteristic curve were put forward in view of the dynamic characteristic behavior of "power-arc-liquid bridge" system, which integrated the expression of different references. Under same welding conditions and parameters, the difference of load voltage-ampere characteristic curve among three welding machines were studied and their welding seam qualities were compared. The results shown that if the load voltage-ampere characteristic curve was closer to the origin of coordinate, welding spatter degree would be smaller. Additionally, the better repeatability of the curve waa, the more stable welding process and the more beautiful welding seam would be. However, if the area enclosed by curves was too large, the possibility of welding defects, such as incomplete fusion and asymmetry of welding seam, would increase.