With the promulgation of the "Pb Restriction Laws" in various countries around the world, Sn-based lead-free solders have been widely studied to replace traditional Sn-Pb solders. However, the development of large-scale integrated circuits and advanced electronic packaging architectures in recent years has placed higher demands on the performance of lead-free solders. This review paper introduced the latest research progress on the main lead-free solder systems such as Sn-Sb, Sn-Cu, Sn-Ag, Sn-Zn, Sn-Bi, and Sn-In systems. And the effects of adding microalloying elements, rare earth elements, and nanoparticles on the microstructure, wettability, mechanical properties, corrosion resistance, and service performance of solder were also reviewed. The main development trends of high-performance lead-free solder were discussed, and innovative research concepts and methods were proposed for the development of next-generation brazing materials.