Abstract: A new low temperature lead-free solder was prepared by adding mass fraction 1%,2%,3% and 4% Bi with 1% Ga to Sn-9 Zn binary alloy,by which the hot dip galvanized 6063 aluminum alloy was soldered. Laser confocal microscope,scanning electron microscope,X-ray diffractometer and Vickers were carried out on the soldered joint to observe microstructure,analyze phase,element distribution and microhardness,respectively. Effects of Bi and Ga element on the interface microstructure and formation mechanism of the soldered joint were studied through comparing with three kinds of traditional lead-containing soldered joints. The results showed that the galvanizing was good at the temperature of 450 ℃ for 10 s,the zinc liquid and 6063 aluminum alloy diffused with each other. The addition of Bi and Ga elements improved the wettability of the solder. Al0.71 Zn0.29 compound particles existed in the soldered joint of Sn-9Zn-xBi-Ga/galvanized layer/6063 aluminum alloy. The maximum microhardness of Sn87 Zn9 Bi3 Ga soldered joint was 38.4 HV0.2 and the soldered joint had the closest metallurgical bond,which was suitable for low temperature soldering of 6063 aluminum alloy.