Abstract: A novel "resistances plug welding" process was used to weld 7075 aluminum alloy lap joints. During resistances plug welding process, a hole was bored at the center of overlapping area of two sheets first, then a cylindrical filler was pressed into the hole, and finally resistance spot welding was used to join the sheets and filler metal together. This process is designed to improve the weld performance of materials which has poor spot weldability. The welding process, nucleation behavior, mechanical properties, and microstructure of resistance plug welding joint were investigated, which was compared with resistance spot welding joint. The results showed that the joint made by this new process had better mechanical properties as well as fewer cracks and other defects.