Lead-free solder powder of Sn-Ag-Cu system was prepared with a supersonic atomizer designed by ourselves. Then the effects of different compositions on the properties of the powder were studied, and the microstructure of its brazed joint was observed, which was compared with that of Sn37Pb solder powder. The results show that the Sn3Ag2.8Cu powder has the highest effective atomization efficiency, the lowest oxygen content, the best sphericity and surface smoothness in the three different compositions powders under the same superheat; the diffusion layer formed between Sn3Ag2.8Cu soldering paste and the copper substrate is thicker and their intermetallics are more irregular than those of Sn37Pb and Sn3Ag2.8Cu-0.1Ce soldering paste; the Sn3Ag2.8Cu-0.1Ce powder has higher effective atomization efficiency and oxygen content than the Sn37Pb powder