Each material has advantages and disadvantages properties, and two different metals, which have advantages properties, were welded to apply its advantages in a construction. Different thermal and electrical properties will influence to a welded joining performance. Aluminum and steel joining by welding process lead to decreasing lap shear strength of welded joint, due to thermal properties. The problem is more complex when the welding process uses thin metal. The objective of this study analyze peak load, elongation, and fracture area (fractographic) from a welded joint between SS301 and AA 1100 with ferro interlayer which was welded by Micro Resistance Spot Welding (RSW). Ferro sheet was inserted between stainless steel and aluminum sheet, RSW machine was used to weld three different plates. Tensile test machine used to measure load and elongation value, and teared plates effected by tensile tested were measured by digital microscope. The highest load value could be achieved by 8 kVA of welding power. Elongation of the highest peak loads was shorter than the lowest peak load. Welding time more than 8 CT tend to produce the elongation become shorter. Welding time affected to decrease fracture area, however welding power has also significantly effect.