Gas metal arc welding (GMAW) of a sub-frame automotive industry was studied, applying a design of experiment (DOE) in Minitab and Matlab software. Voltages, welding speed and wire feed speed was defined as input variables; legs and throats of welding were output variables in millimeters dimension. The requirement for GMAW process was to achieve complete penetration, minimum values acceptable of legs and throat indicated in AWS D8.8M:2007 “Specification for automotive weld quality-arc welding” without any discontinuity, like undercutting or porosity. The required of quality were difficult to achieve due to the materials have microstructural and mechanical properties different, the SAE 1008 has 279MPa for ultimate tensile strength (UTS) and the microstructure consist of ferrite matrix with some small areas of cementite, while SAE 2340 has 456MPa of UTS with a combination of perlite and ferrite. It was possible obtain good quality welds with proper geometry and defect free with help to design of experiment. The conditions needed were a combination of parameters to not obtained significant change microestructural characterized by optical microscopy, stereoscopy and scanning electron microscopy.