The wettability of the solders Zn-25Sn-XAl (x=0-0.09wt%) was investigated by dipping method. The interfaces between solders and Cu substrate were investigated by scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and energy dispersive spectroscopy (EDS) equipped in transmission elctron microscopy (TEM). It was found that the addtion of Al enhances the wettability of the solders on Cu. The three layers (Cu,Al)Zn, (Cu,Al)5Zn8 and (Cu,Al)Zn5 were found at the interfaces between Cu substrate and solders. The thickness of intermetallic compounds layers increased with Al additions. The higher Al addition, the higher Al intetnsity was detected in the intermetallic compounds layer. The Al addition exhibits two stages behaivor on both wetting time and interfacial intermetallic growth.