The sheet metal parts play important role in aero structures. Due to the requirement of strength and constraint of weight in aircraft, the aluminum alloy is widely used in sheet metal forming parts. Most of sheet metal parts form the contour in O-condition, and then solution treat to improve the strength and mechanical property. The deformation of sheet metal parts usually takes place after the heating cycle and quenching into the water or solution. The straightening operation will apply to corrective the contour of parts. Thus, the non-value added operation would increase the production cost. By using statistical methodology to analysis deformation data of sheet metal parts, this study use Cause-Effect Analysis to find the relation between deformation and relative factors, such as material, thickness and contour. The results of this analysis can provide an efficient and economical approach for the designer, process planner, and technician in manufacturing the sheet metal parts.