In the process of the pulse MIG power supply welding, the arc length will change dynamically due to various environmental disturbances. Therefore, how to realize the real-time control of the arc length is the key to the stability of the pulse MIG welding process, and it is also an important guarantee of the welding quality. In this paper, the three voltage loop control methods of no arc length control, one-dimensional fuzzy control and two-dimensional fuzzy control are compared through matlab simulation. The simulation results show that the arc length control scheme of welding power supply based on two-dimensional fuzzy control can achieve better dynamic response when the stepwise mutation occurs in the arc length.