Aimed at reduced spattering and better weld formation, we adopted a refined method of current waveform control, and reported a model for GMAW comprising four modules that were inverter power supply, arc load, wire feeder system and waveform control system. SIMULINK tools of MATLAB were implemented to establish this model, and the simulation results were compared with our experiments to comprehensively evaluate the influence of the large constant current and the small constant current of arc stage on the welding outcomes. In the short circuit transfer process, the base short-circuit current duration and the peak short-circuit current had great impacts on spatter generation whereas the effect of the current surge rate was relatively small within a certain range. Parameters of waveform control method we obtained and optimized based on this model were confirmed effective and efficient for a high stability of welding process.