Abstract: Research work of wire extension control based on vision sensing was done in pulsed MIG welding process of aluminum alloy. A rapid prototyping control platform was established for pulsed MIG welding of aluminum alloy using real-time target environment based on xPC. With vision sensing of welding zone image and corresponding image processing algorithm, a fuzzy PID closed loop control system for wire extension was designed on the basis of the built rapid prototyping control platform. Then experimental results show that the method of vision sensing can meet the control requirements of wire extension stability, the rapid prototyping control system built with fuzzy PID controller based on vision sensing can realize the well control of the wire extension in pulsed MIG welding of aluminum alloy and also has strong robustness and quick response ability.