Because customers are requiring front-loaded washing machine to handle big capacity laundry and have faster rotation speed to increase drying ability, there are being a lot of studies for achievement of high speed dehydration, high-strength and lightweight of washing machine in the latest washing machine business. It is essential that strength of Drum Assembly which is composed of spin drum, shaft, flange is improved to attain that target. In term of spin drum, it is difficult to realize joint strength required at high speed operation because joint strength of mechanical press-joining method is low remarkably in comparison with welding. Also in case of shaft system, stress from bending and twisting are complexly loaded onto the shaft supporting the horizontal drum, causing problems in fracture strength and fatigue life. The results of this study show optimal joining condition for mechanical press-joining by performing lots of tensile joining strength test with various specimen under multi-change of important design factor such as seaming width, bead area and bead depth etc. and the optimal design of shafting system for big capacity, high-rotation drying through strength analysis, experiment and evaluation.