Abstract: In order to study the influence of narrow groove on the welding process, the numerical simulation of GMAW systems based on the oscillating arc sensor has been studied according to the principle of weding energy balance and droplet balance. The mathematical model of four subsystems, including a welding torch oscillation, an arc length, nonlinear arc load and arc welding power source arc, has been built according to the size of the torch height is changing with torch oscillation in the groove. And the mathematical model is transformed into a GMAW system dynamic characteristic simulation model which covers the whole welding loop under Matlab/simulink environment. The results show that when the welding parameters are the same, by operating the system simulation model, the data of the current and voltage waveforms can be obtained which are basically the same as the actual experiments.