Abstract: As electronic packaging technology advances toward higher integration, miniaturization, and enhanced reliability, traditional lead-free solders face numerous challenges in mechanical properties, wettability, and thermal stability. Nanoparticle-reinforced composite solders, owing to their unique size effects, high specific surface area, and interfacial activity, demonstrate significant advantages in refining microstructure, enhancing mechanical properties, and suppressing excessive intermetallic compound (IMC) growth. This makes them a crucial approach for optimizing lead-free solder performance. This paper systematically reviews recent preparation methods for nanoparticle-reinforced lead-free composite solders, including mechanical blending, ultrasonic-assisted methods, self-propagating particle formation, and electrochemical deposition. It focuses on analyzing the principles, process characteristics, and effects on solder microstructure and properties of each method. It also summarizes current challenges in preparation techniques, such as particle agglomeration, poor interfacial wettability, complex processes, and high costs, while outlining future development directions. This review aims to provide theoretical foundations and technical references for the development of high-performance green packaging materials.