Abstract: Mathematical model of the burning arc and short circuit stage for CO₂ shielded arc welding and related power source-load simulation model were set up. The closed-loop control structure was adopted in the study, in which the current and arc voltage were uninterrupted switching. Namely, the constant voltage control was applied at the end of burning arc stage, and the current control of given STT (surface tension transition) current waveform was applied at the other stage. The fuzzy neuron PI controller of current and arc voltage was designed. The simulation platform for CO₂ shielded arc welding inverter power source control system was established. Simulation results show that the closed-loop control structure and control algorithm proposed in the study can make the welding current more close to the ideal STT current waveform. It can improve the appearance of welding and realize transition without splash. The invariable arc voltage at the end of burning arc can make the arc self-regulation characteristics better.