To address the problem of floating and aggregation of Ag-GNSs in the molten pool during the traditional reflow soldering process, Cu/SAC/Ag-GNSs/Cu sandwich joints were prepared under an applied current density (1.0×10⁴ A/cm²) for a few hundred milliseconds to produce Ag-coated graphene-reinforced Sn-Ag-Cu (SAC/Ag- GNSs) solder joints. The experimental results showed that Ag-GNSs were homogenously dispersed in the solder joints, providing more Cu₆Sn₅ grain nucleation sites, which refined these grains and reduced the thickness difference at the anode and cathode. In addition, the Cu₆Sn₅ morphology changed from rod-like to plate-shaped because of the uniform distribution of Ag-GNSs and constitutional supercooling. The significantly increased shear strength of the transient current bonding and the change in the fracture mechanism were due to the uniformly distributed Ag-GNSs and the microstructural changes.