Cold metal transfer with polarity?exchanging is a new integrated welding technology based on MIG. Due to the alternation of the positive and negative polarities of the wire, favorable control upon the deposition rate and the welding shape coefficient was obtained in order to meet the desired joint design, and the related controlling principles and joint characteristics were reported. Droplet transfer physical behavior exhibited strong dependability on the studied welding parameters, such as welding voltage, welding current, wire feeding speed, and polarity?exchanging. This welding technology provides a new way for the welding of body?in?white ( BIW) thin sheet with special demands. Moreover, the typical quality defects of MIG were greatly improved. Our study provides important technical information from the perspective of industrial application of MIG and sheds light on the higher application level of MIG in BIW welding.