Abstract: Considering the characteristics of aluminum alloy MIG welding process, nine-point controller was developed to control weld pool width.The structure and the principle of nine-point controller were analyzed.Based on the mathematic model of step response between pulse current and weld pool width, the simulations on three controlles of PID, fuzzy and nine-point controller used to control aluminum alloy MIG weld pool width were studied.The simulation results show that nine-point controller not only has the best stability and robust than PID and fuzzy controller, but also assure the control accuracy and provides the theoretical basis to realize the intelligent control for aluminum alloy pulsed MIG welding process.