Abstract: Effects of Ga on melting characteristics and wetting properties of Sn-9Zn lead-free solder as well as the mechanical properties of the soldered joints were investigated, respectively.The results indicate that the melting point of Sn-9Zn lead-free solder decreases obviously, the melting range increases and the wettability is gradually improved with the addition of Ga.When the content of Ga is around 0.5 wt.%, the grains of microstructure are the finest and the most homogeneous, the best mechanical property of soldered joint is obtained.When the content of Ga is above 1wt.%, the wettability tends to be stable, some Ga-rich phases appear on the grain boundaries and the mechanical property of the soldered joint decreases sharply.In general, the optimum additive amount of Ga in Sn-9Zn solder is about 0.5 wt.%.