Abstract: Al-alloys are major materials in fabricating high-speed locomotive and rolling stock.Al-alloys have special requirements on MIG welding due to their unique physical and chemical properties.A new welding machine was developed and it generated pulsed current to control the mode of metal transfer in Al-alloys MIG welding.During the entire range of welding current,the droplet transfer was achieved.As a result of this,welding arc had a good stiffness and droplet transfer was very stable.Since pulse parameters were controlled only by one knob,the operation of the machine was very easy.Once the wire feed speed was set,other parameters were established automatically in the welding machine.Because the Al-alloys MIG welding had different dynamic requests in different states,the "Self-Adjusted Dynamics" concept was put forward,which was achieved through the dynamic electronic inductor and the short circuit current controller.In addition,the machine could feed wire at a pulsed speed,so that puddle was well controlled and a smooth bead was formed.