Abstract: Diode laser soldering system was used to study and explore the ways to improve the wettability of Sn96Ag3.5Cu0.5 lead-free solder and Sn63Pb37 solder in the contrast experiments, the effects of laser output power on the wettability of solders on copper were also analyzed in this paper. Results indicate that increasing diode laser output power can greatly improve the wettability of Sn96Ag3.5Cu0.5 lead-free solder and Sn63Pb37 solder in a certain range. According to different alloy components and flux components in the solder pastes, optimizing laser soldering parameters, the optimal soldered joints can be obtained and the results will provide a novel method for improving the wettability of Sn96Ag3.5Cu0.5 lead-free solder.