Abstract: In order to solve the problem of poor stability of the microstructure and mechanical properties of Sn58Bi welded joints in the aging stage, the effect of Ni particles (50 nm) alloying on the microstructure and mechanical properties of Sn58Bi welded joints is studied. The results of the study show that, in the aging reaction stage, IMC barrier layer will be generated in the composite solder, the phase transition of Cu6Sn5 to Cu3Sn is suppressed, which makes the Bi phase unable to segregate to the brazing junction through the phase change process, so that the microstructure stability of Sn58Bi-Ni solder welding seam is overall improved. With the addition of Ni particles in the Sn58Bi solder,the nucleation rate of Bi phase was improved, and the local microstructure of solder was refined, and the segregation of pure Bi and pure Sn phase was inhibited, and the stability of the internal structure of solder was improved. When the content of Ni is about 0.5wt%, the mechanical properties of Sn58Bi-Ni composite solder is the best.