Abstract: Using different diode-laser soldering parameters, soldering experiments of Sn-Ag-Cu lead-free solder was carried out on Cu substrate using diode-laser soldering system, and the forming rules of the intermetallic compound were also analyzed in Sn-Ag-Cu soldered joints.The results show that, when the laser soldering time is 1s and the laser output power is 38.3W, the mechanical properties of soldered joints are the best.With the change of laser soldering parameters, microstructures of soldered joints are relevantly changed.With the optimum laser soldering parameters, microstructures of soldered joint are fine and no excessive grow of Cu₆Sn₅ intermetallic compound, and the appropriate thickness of Cu₆Sn₅ layer is also got.Competitive experiments results show the intermetallic compound layer with laser soldering system is smoother than that with the IR soldering method, and the excellent mechanical properties can be abtained for the soldered joints.