Abstract: The metal transfer behavior of meso-spray transfer is studied under self-adapting control of meso-spray in pulse MIG welding of aluminum.The main acting forces against a droplet and the important role of surface tension are analyzed by the waves testing and high speed camera of short circuit, meso-spray and spray from different parameters in pulse MIG welding.The results of experiment demonstrate that a self-adapting process should be accurately controlled for the narrow working range of meso-spray transfer in pulse MIG welding of aluminum, and the proposed control parameters can make the arc running within the narrow range and the special droplet transfer process stable.