Abstract: A dynamic mathematical model for welding arc was developed by adopting the method of equivalent current path according to the arc dynamic characteristics of DE-GMAW process and the rule of wire-melting.Based on that,simulations about non-consumable DE-GMAW and consumable DE-GMAW were carried out by MATLAB/Simulink.Then the influence of welding torches angle on stability of DE-GMAW process was simulated and analyzed.The results show that the developed mathematical model can reflect the DE-GMAW process well.When the angel between main and bypass torch is 45°,the response time for welding process to achieve stability is the shortest and is consistent with the actual welding process and the non-consumable DE-GMAW is much more stable than consumable DE-GMAW.