Abstract: Shielded metal arc welding inverter and the arc load is a typical kind of non linear system,it's difficult to establish a model and find accurate transient response solution.Moreover,other simulation methods can only get approximate solution within small signal range.Simulink software is superior for simulating this kind of system.We setup a Simulink simulation model for SMAW inverter,especially the PWM model and arc load model.The relation between voltage,current,arc height and time is studied by simulation.Using LEM sensor and scope that can store data experiment results obtained are consistent with simulation results.So the model is very useful for studying SMAW inverter.