DE-GMAW (Double-Electrode Gas Metal Arc Welding) is a new welding technology. It is possible to change the melting current while the base metal current still be controlled at a desired level because the changed part of the melting current would be bypassed without flowing through the workpiece. So the heat input of base metal can be controlled accurately in DE-GMAW, and this welding method is suitable for dissimilar metal welding which has strict requirements for heat input of base metal, such as joining of steel and aluminum. On the basis of heat source model of DE-GMAW, numerical simulation and analysis on temperature field and residual stress for DE-GMAW in bonding steel and aluminum were done. The results show that residual stress after welding changed sharply from close 0 MPa to about 130 MPa at the interface of aluminum and steel. This value is greater than the binding force of steel, aluminum interface.