Abstract: It is difficult to study and design the CO₂ arc welding power source-arc system due to the short transfer of CO₂ arc welding which has nonlinear and instanganeous characteristics.This paper studies the dynamic process of the CO₂ arc welidng inverter-arc system based on the modeling of welding arc and the modeling of welding inverter-arc system with MATLAB.At the same time,several representative waves of arc are showed on the simulation scope.A new concept called balance length is put forward.The balance length should be designed between 0 mm and several millimeters (this numerical value is accordance to the welding parameter).A type of wave-controlled CO₂ arc welding inverter-arc is simulated to disclose the effect of the inverter-arc system control parameters on the CO₂ welding process for optimizing the system design.