Abstract: By means of welding power system circuit model, thinking of the enthalpy changes on the wire tip, and energy balance on the droplet, the more precise CO₂ short circuit transfer dynamic simulation model is put forward. Through this model, it explores changing trend of current waveform, and makes a comparison of characteristic parameters (average current, peak current, valley current, short circuit frequency, short circuit time and arcing time) between the practical measurement and the simulation under matching and mismatching welding parameters. And the related deviations of the characteristic parameters are analyzed. The results indicate that the model is basically consistented with practice. At last, this research will contribute to further development of simulation in short circuit transfer process.